Genetics: A Conceptual Approach, 5th Edition

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With Genetics: A Conceptual Approach, Ben Pierce brings a master teacher’s experiences to the introductory genetics textbook, clarifying this complex subject by focusing on the big picture of genetics concepts and how those concepts connect to one another. The new edition features Pierce's signature writing style, relevant applications, student-friendly art, and emphasis on problem-solving, while incorporating the latest trends in genetics research. The new edition text and LaunchPad media work closely together for a seamless experience for both instructors and students.

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A Conceptual Approach FIFTH EDITION

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Contents in Brief 1. Introduction to Genetics 1 2. Chromosomes and Cellular Reproduction 17 3. Basic Principles of Heredity 45 4. Sex Determination and Sex-Linked Characteristics 77 5. Extensions and Modifications of Basic Principles 103 6. Pedig ree Analysis Applications and Genetic Testing 139 7. Linkage Recombination and Eukaryotic Gene Mapping 165 8. Chromosome Variation 209 9. Bacterial and Viral Genetic Systems 241 10. DNA: The Chemical Nature of the Gene 277 11. Chromosome Structure and Organelle DNA 299 12. DNA Replication and Recombination 325 13. Transcription 357 14. RNA Molecules and RNA Processing 383 15. The Genetic Code and Translation 411 16. Control of Gene Expression in Bacteria 443 17. Control of Gene Expression in Eukaryotes 473 18. Gene Mutations and DNA Repair 493 19. Molecular Genetic Analysis and Biotechnology 535 20. Genomics and Proteomics 579 21. Epigenetics 613 22. Developmental Genetics and lmmunogenetics 633 23. Cancer Genetics 661 24. Quantitative Genetics 683 25. Population Genetics 715 26. Evolutionary Genetics 743 Reference Guide to Model Genetic Organisms A1

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Letter fron1 the Author XV Preface xvi Contents Chapter 1 Introduction to Genetics i Albinism in the Hopis 1 1.1 Genetics ls lmportantto Us Individually to Society and to the Study of Biology 2 The Role of Genetics in Biology 4 Crenetic Diversity and Evolution 4 Divisions of Genetics 5 Model Genetk Organisms 5 1.2 Humans Have Been Using Genetics for Thousands of Years 7 The Early Use and Understanding of Heredity 7 The Rise ofthe ScienceofGenetks 9 The Future of C.enetics 10 1.3 A Few Fundamental Concepts Are Important for the Start of Our Journey into Genetics 11 Chapter 2 Chromosomes and Cellular Reproduction 11 The Blind Mens Riddle 17 2.1 Prokaryotic and Eukaryotic Cells Differ in a Number of Genetic Characteristics 18 2.2 Cell Reproduction Requires the Copying of the Genetic Material Separation of the Copies and Cell Division 20 Prokaryotic Cell Reproduction 20 Eukaryotk Cell Reproduction 20 The Cell Cycle and Mitosis 23 C.enetic Comequences of the CeU Cycle 26 CONNECTING CONCEPTS Counting Chromosomes and DNA Molecules 27 2.3 Sexual Reproduction Produces Genetic Variation Through the Process of Meiosis 27 Meiosis 28 Sources of Genetic Variation in Meiosis 31 CONNECTING CONCEPTS Mitosi. s and M eiosis Compared 33 The Separation of Sister Chromatids and Hon1ologous Chron1 oson1 es 3 3 Meiosis in the Life Cycles of Animals and Plants 35 Chapter 3 Basic Principles of Heredity 45 The Genetics of Red Hair 45 3. 1 Gregor Mendel Discovered the Basic Principles of Heredity 46 MendeliSu ccess 47 Genetic Terminology 48 3.2 Monohybrid Crosses Reveal the Principle of Segregation and the Concept of Dominance 49 What Monohybrid Crosses Reveal 5 0 CONNECTING CONCEPTS Relating Geneti c Crosse s to Meiosis 52 The Molecular Nature of Alleles 5 3 Predicting the Outcon1es of Genetic Cros..ies 53 The Testcross 57 Genetk Symbols 58 CONNECTING CONCEPTS Ratios in Simple Crosses 58 3.3 Dihybrid Crosses Reveal the Prindple of Independent Assortment 5 9 Di hybrid Crosses 59 The Principle of Independent Assortment 59 Relating the Principle of Ind ependent Assortment to Meiosis 60 Applying Probability and the Branch Diagram to Di hybrid Crosses 61 The Di hybrid Testcross 62 3.4 Observed Ratios of Progeny May Deviate from Expected Ratios by Chance 64 The Goodness-of-Fit Chi-Squ are Test 6 4 v

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Chapter 7 Linkage Recombination and Eukaryotic Gene Mapping 165 Linked Genes and Bald Heads 165 7.1 linked Genes Do Not Assort Independently 166 7.2 linked Genes Segregate Together and Crossing OVer Produces Recombination Between Them 167 Notation for Crosses with Linkage 168 Complete Linkage Compared with Independent Aortment 168 Crossing Over with Linked Gen es 170 Calculating Recombination Frequency 171 Coupling and Repulsion 172 CONNECTING CONCEPTS Relating Independent Assortment linkage and Crossing over 173 Evidence for the Physical Basi.s of Recombination 174 Predicting th e Outcomes of Crosses with Linked C.enes 175 Testing for In dependent Aortment 176 Crene lvfapping \\ith Recon1bination Frequencies 178 Omstructing a C.enetic Map with the Use of T\.o PointTestcros.ses 179 7 3 A Three-Point Testcross Can Be Used to Map Three Linked Genes 180 Constructing a Genetic. Ylap \.ith the Three .. Point Testcross 181 CONNECTING CONCEPTS Stepping Through the Three-Point Cross 186 Effect of Multiple Cxossovers 188 Mapping Human Genes 189 lvapping with Molecular Markers 190 Cenes Can Be Located \\Tith Genon1ee AssodationStud ies 191 7 .4 Physical-Mapping Methods Are Used to Determine the Physical Positions of Genes on Particular Chromosomes 192 Somatic· Cell Hybridization 192 Deletions Mapping 194 Physical Chromosome Mapping Through Molecular Analysis 195 7.5 Recombination Rates Exhibit Extensive Variation 195 Chapter 8 Chromosome Variation 209 Building a Better Banana 209 8.1 Chromosome Mutations Include Rearrangements. Aneuploids and Polyploids 210 Chromosome Morphology 210 Types of Chron1oson1e Mutations 211 8.2 Chromosome Rearrangements Alter Chromosome Structure 212 Duplications 212 Deletions 214 Inversions 216 Translocations 219 Fragile Sites 221 Copy-Number Variations 222 Contents vii 8.3 Aneuploidy ls an Increase or Decrease in the Number of Individual Chromosomes 222 Types of Aneuploidy 222 Effectsof Aneuploidy 223 Aneuploidy in Humans 224 Uni parental Dinmy 22 7 Mosaicism 228 8.4 Polyploidy Is the Presence of More than Two Sets of Chromosomes 228 Autopolyploidy 228 Allopolyploidy 229 The Significanceof Polyploidy 232 Chapter 9 Bacterial and Viral Genetic Systems 241 Life in a Bacterial World 241 9.1 Genetic Analysis of Bacteria Requires Special Methods 242 Bacterial Diversity 242 Techniques for t he Study of Bacteria 243 The Bacterial Genome 244 Plasmids 245 9.2 Bacteria Exchange Genes Through Conjugation Transformation and Transduction 247 Conjugation 247 Natural Gene Transfer and Antibiotic Resistance 254 Transforn1ation in Bacteria 25 4 Bacterlal Genon1 e Sequences 256 Horizontal Gene Transler 256 v

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viii C ontents 9.3 Viruses Are Simple Replicating Systems Amenable to Genetic Analysis 257 Tech niques for the Study of Bacterioph age. 25 7 Transduction: Using Phages to lvap Bacterial Genes 258 CONNECTING CONCEPTS Three Methods for Mapping Bacterial Gen tS 261 Gene Mapping in Phages 261 Fine-Structure Analysis of Bacteriophage Genes 263 RNA Viruses 265 Human Immunodeficiency Virus and AIDS 267 l nfluenz. a 268 Chapter 10 DNA: The Chemical Nature of the Gene 277 Arctic Treks and Ancient DNA 277 10.1 Genetic Material Possesses Several Key Characteristics 278 10.2 All Genetic Information Is Encoded in the Structure of DNA or RNA 278 EarlyStudiesof DNA 278 DNA As the Source of Genetic InlOrmation 280 \iVatson and Crkks Diic.overy of the Three .. Dimensional Structure of DNA 283 RNA As Genetk Material 285 10.3 DNA Consists of Two Complementary and Antiparallel Nucleotide Strands That Form a Double Helix 286 The Primary Structure of DN A 286 Secondary Structures of DNA 288 CONNECTING CON CEPTS Genetic Implications of DNA St ructure 290 10.4 Special Structures Can Form in DNA and RNA 291 Chapter 11 Chromosome Structure and Organelle DNA 299 Telomeres and Childhood Adversity 299 11.1 Large Amounts of DNA Are Packed into a Cell 300 Supercoiling 300 The Bacterial Chromosome 301 Eukarrotic Chron1oson1 es 302 Changes in Chromatin Structure 304 11.2 Eukaryotic Chromosomes Possess Centromeres and Telomeres 306 Centmn1ere Structure 306 TelomereStructure 307 11.3 Eukaryotic DNA Contains Several Classes of Sequence Variation 308 The Denaturation and Renaturation of DNA 308 Types of DNA Sequences in Eukaryotes 308 11.4 Organelle DNA Has Unique Characteristics 309 Mitochond rion and Chloroplast Structur e 309 The Endosymbiotic Theory 310 Uniparental In heritance of Organelle· Encoded T raits 31 1 The Mitochon drial Genome 314 The Evolution oflvlitochondrial DNA 316 Damage to Mitochondrial DNA ls Associated with Aging 316 The Chloropla. st Genome 317 Through Evolutionary Tin1 e. Genetk Jnf0rn1ation Has rvtoved Bet\leen Nuclear lvlitochondr ial and Chloroplast Genome. 318 Chapter 12 DNA Replication and Recombination 325 Topoisomerase Replication and Cancer 325 12.1 Genetk Information Must Be Accurately Copied Every Time a Cell Divides 326 12.2 All DNA Replkation Takes Place in a Semiconservative Manner 326 Meselson and Stahl Eleriment 327 Mode.of Replb tion 329 Requirements of Replication 332 Direction of Replication 332 CONNECTING CONCEPTS The Direction of Synthesis in Different Models of Replicati on 334 12.3 Bacterial Replication Requires a Large Number of Enzymes and Proteins 334 Initiation 334 Unwinding 33 4 Elongation 336 Termination 339 The Fidelity of DNA Replkation 339 CONNECTING CONCEPTS The Basic Rules of Replication 340

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12.4 Eukaryotic DNA Replication Is Similar to Bacterial Replication but Differs in Several Aspects 340 Eukaryotic Origins 340 The Licensing of DNA Replication 341 Unwinding 341 Eukaryotic DNA Polymerases 341 Nucleo.son1e As.en1bly 342 The Location of Replication \lithin the Nucleus 343 DNA Synthesis and the CeU Cycle 343 Replication at the Ends of Chron1oson1e.s 344 Replication in Archaea 346 12.5 Recombination Takes Place Through the Breakage Alignment and Repair of DNA Strands 346 Models of Recombination 347 Enzymes Required for Recombination 348 Crene Conversion 349 Chapter 13 Transcription 357 Death Cap Poisoning 357 13.1 RNA . • Consisting of a Single Strand of Ribonucleotides Participates in a Variety of Cellular Functions 3 58 An Early RNA World 358 The Structure of RNA 3 58 Classes of RNA 359 13.2 Transcription Is the Synthesis of an RNA Molecule from a DNA Template 360 The Template 361 The Substrate for Transcription 363 The Transcription Apparatus 363 13.3 Bacterial Transcription Consists of Initiation Elongation and Termination 365 Initiation 365 Elongation 367 Ternlination 368 CONNECTING CONCEPTS The Basic Rules of Transcription 369 13.4 Eukaryotic Transcription Is Similar to Bacterial Transcription but Has Some Important Differences 370 Transcription and Nucleoson1eStructnre 370 Promoters 3 70 Initiation 371 Elongation 373 Termination 373 Contents ix 13.5 Transcription in Archaea Is More Similar to Transcription in Eukaryotes Than to Transcription in Eubacteria 374 Chapter 14 RNA Molecules and RNA Processing 383 A Royal Disease 383 14.1 Many Genes Have Complex Structures 384 Gene Organiztion 384 lntrons 385 The Concept of the Gene Retisited 387 14.2 Messenger RNAs. Which Encode the Amino Acid Sequences of Proteins Are Modified after Transcription in Eukaryotes 387 The Structnre of Messenger RNA 387 Pre· mRNA Processing 388 The Addition of the 5 1 Cap 388 The Addition of the Poly A Tail 389 RNA Splicing 390 Alternative Processing Path\lays 393 RNA Editing 3 95 CONNECTING CONCEPTS Eukaryotic Gene Structure and Pre·mRNA Processing 396 14.3 Transfer RNAs Which Attach to Amino Acids Are Modified after Transcription in Bacterial and Eukaryotic Cells 397 The Structure of Transfer RNA 398 Transfer RNA Cene Structure and Processing 399 14.4 Ribosomal RNA a Component of the Ribosome. Is Also Processed after Transcription 400 The Structnre of the Ribosome 400 Ribosomal RNA Gene Structure and Processing 401 14.5 Small RNA Molecules Participate in a Variety of Functions 402 Ri"JA Interference 402 Small Interfering and Micro RNAs 403 Piwi·I nteracting RNAs 404 CRISPR RNA 404 14.6 Long Noncoding RNAs Regulate Gene Expression 405

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x Contents Chapter 15 The Genetic Code and Translation 411 Hutterites Ribosomes and Bowen-Conradi Syndrome 4 11 15.1 Many Genes Encode Proteins 412 The One Gene One Enzyme Hypothesis 412 The Structure and Function of Proteins 415 15.2 The Genetic Code Determines How the Nucleotide Sequence Specifies the Amino Acid Sequence of a Protein 41 7 Breaking the Genetic Code 418 The Degeneracy of the Code 420 The Reading Frame and Initiation Codons 421 Termination Codons 422 The Universality of the Code 422 CONNECTING CONCEPTS Characteristics of the Genetic Code 422 15.3 Amino Acids Are Assembled into a Protein Through Translation 422 The Binding of Amino Acids to Transfer IU1As 423 The Initiation of Translation 424 Elongation 426 Termination 427 CONNECTING CONCEPTS A Comparison of Bacterial and Eukaryotic Translation 430 15.4 Additional Properties of RNA and Ribosomes Affect Protein Synthesis 430 The Three· Dinlensional Structure of the Ribosome 430 Polyribosomes 43 1 Messenger RNA Surveillance 431 Folding and Posttranslational Modifictions of Proteins 433 Translation and Antibiotics 433 Chapter 16 Control of Gene Expression in Bacteria 443 Operons and the Noisy Cell 443 16.1 The Regulation of Gene Expression Is Critical for All Organisms 444 Genes and Regulatory Element 445 LeveLrnfGene Regulation 445 DNA-Bind ing Proteins 446 16.2 Operons Control Transcription in Bacterial Cells 447 Operon Structure 447 Negative and Positive Control: Inducible and Repressible Operons 448 The lac Operon of E.coli 450 lac Mutations 453 Positive Control and Catabolite Repression 457 The tr p Operon of E. e-0/i 458 Bacterial Enhancen 460 16.3 Some Operons Regulate Transcription Through Attenuation the Premature Termination of Transcription 460 Attenuation in the trp Operon of E. coli 460 Why Does Attenuation Take Place in the trp Operon 464 16.4 RNA Molecules Control the Expression of Some Bacterial Genes 464 AntLense RNA 464 Riboswitch es 464 RNA-Mediated Repres_on Throug h Ribozymes 466 Chapter 17 Control of Gene Expression in Eukaryotes 473 Genetic Differences That Make Us Human 473 17. 1 Eukaryotic Cells and Bacteria Have Many Features of Gene Regulation in Common but They Differ in Several Important Ways 474 17.2 Changes in Chromatin Structure Affect the Expression of Genes 474 DNase I Hypersensitivity 474 Chromatin Remodeling 475 Hitone Modification 475 DNA Methylation 478 17.3 The Initiation of Transcription Is Regulated by Transcription Factors and Transcriptional Regulator Proteins 479 Transcriptional Activators and Coactivators 479 Transcriptional Repressors 481 Enhancers and lnsulaton 481 Regulation of Transcriptional Stalling and Elongation 482 Coordinated Gene Regulation 482 17.4 Some Gen es Are Regulated by RNA Processing and Degradation 483 Gene Regulation Through RNA Splicing 483 The Degradation of RNA 484 17.5 RNA Interference Is an Important Mechanism of Gene Regulation 485 Small Interfering RNAs and MicroRNA. 485

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Mechanisms of Gene Regulation by RNA Interference 486 The C.ontrol of Development by RNA Interference 487 17.6 Some Genes Are Regulated by Processes That Affect Translation or by Modifications of Proteins 487 CONNECTING CONCEPTS A Compa rison of Bacterial and Eukaryotic Gene Control 488 Chapter 18 Gene Mutations and DNA Repair 493 A Fly Without a Heart 493 18.1 Mutations Are Inherited Alterations in the DNA Sequence 494 The Importance of Mutations 494 C"..ategories of Mutations 494 Types of C.ene Mutations 495 Phenotypic Effects of Mutations 497 Suppressor Mutations 498 Mutation Rates 502 18.2 Mutations Are Potentially Caused by a Number of Different Factors 503 Spontaneous Replkation Error. 503 Spontane.ous Chemical Changes 504 ChemicaUy Induced Mutations 506 Radiation 508 18.3 Mutations Are the Focus of Intense Study by Geneticists 509 Detecting Mutations \lith the An1es Test 509 Radiation Exposure in Hun1ans 510 18.4 Transposable Elements Cause Mutations 511 C.eneral Characteristics of Transposable Element 5 11 Transposition 512 The Mutagenic Effects of Transposition 513 Transposable Elements in Bacteria 514 Transposable Elements in Eukaryotes 515 CONNECTING CONCEPTS Types ofTransposable Elements 519 Transposable Elements Have Played an ln1portant Role in Genon1 e Evolution 520 18.5 A Number of Pathways Repair Changes in DNA 520 lvfismatch Repair 520 Direct Repair 522 Ba.e· Excision Repair 522 Nucleotide-Excision Repair 523 CONNECTING CONCEP TS The Basi c Pathway of DNA Repair 524 Repair of Doubte 5trand Breaks 524 Translesion DNA Polymerases 524 Contents xi Genetic Dleases and Faulty DNA Repair 525 Chapter 19 Molecular Genetic Analysis and Biotechnology 535 Helping the Blind to See 535 19.1 Techniques of Molecular Genetics Have Revolutionized Biology 536 The Molecular C.enetics Revolution 536 Working at the Molecular Level 536 19.2 Molecular Techniques Are Used to Isolate Recombine and Amplify Genes 537 Cutting and Joining DNA Fragment 537 Viewing DNA Fragments 539 Locating DNA Fragment with Southern Blotting and Probes 540 Cloning Genes 541 Application: The Genetic Engineering of Plant with Pestkides 545 Amplifying DNA Fragments with the Polymerase Chain Reaction 546 19.3 Molecular Techniques Can Be Used to Find Genes of Interest 549 Gene Libraries 549 In Situ Hybridization 552 Positional Cloning 552 Application: lolating the Gene for Cystk Fibrosl 553 19.4 DNA Sequences Can Be Determined and Analyzed 555 Restriction Fragment Length Polymorphisms 555 DNA Sequencing 556 Next-Generation Sequencing Technologies 559 DNA Fingerprinting 561 Application: Identifying People Who Died in the Collapse of the World Trade Center 562 19.5 Molecular Techniques Are Increasingly Used to Analyze Gene Function 563 Forward and Reverse Genetics 563 Creating Random Mutations 564 Site-Directed Mutagenesis 564 Transgenic Animals 565 Knockout Mke 566 Silencing Genes with RNAi 567 Application: Using RllAi to Treat Human Disease 568

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xii C ontents 19.6 Biotechnology Harnesses the Power of Molecular Genetics 569 Pharmaceutical Produrn 569 Specialized Bacteria 569 Agrkultural Products 569 Genetk Testing 570 Gene Therapy 571 Chapter 20 Genomics and Proteomics 579 Decoding the Waggle Dance: The Genome of the Honeybee 579 20. 1 Structural Genomics Determines the DNA Sequences of Entire Genomes 580 Genetk Maps 580 Physkal Maps 581 Sequencing an Entire Genome 582 The Human Genome Project 583 Single-Nucleotide Polymorphisms 587 Copy· Number Variations 588 Sequence-Tagged Sites and Expressed ..Sequence Tags 589 Bioinformatics 589 Metagenomics 590 Synthetk Biology 591 20.2 Functional Genomics Determines the Function of Genes by Using Genomic-Based Approaches 591 Predicting Function from Sequ ence 591 Gene E.Xpression and 1icroarrays 592 Gene Expression and Reporter Sequences 595 Genon1e .. \\ide Ylutagenesis 595 20.3 Comparative Genomics Studies How Genomes Evolve 596 PmkaryoticGenomes 596 Eukarrotic Cenon1es 598 Con1parative Drosophila Genon1ks 601 The Human Genome 601 20.4 Proteomics Analyzes the Complete Set of Proteins Found in a Cell 603 Determination of Cellular Proteins 603 Affinity Capture 604 Protein Mkroarrays 604 Structural Proteon1ics 605 Chapter 21 Epigenetics 613 How Your Grandfathers Diet Could Affect Your Health 613 21. 1 What Is Epigenetics 614 21.2 Several Molecular Processes Lead to Epigenetic Changes 615 DNA Methylation 615 H istone Modifications 617 Epigenetic Effects by RNA Molecules 618 21.3 Epigenetic Processes Produce a Diverse Set of Effects 619 Paran1utation 619 Behavioral Epigenetks 621 Epigenetic Effects of Environmental C.hemical 623 Transgenerational Epigenetic Efticts on Metabolism 623 Epigenetic Effects in Monozygotic Twins 623 X Inactivation 623 Epigenetic Changes Associated with Cell Differentiation 625 Genomk Imprinting 626 21.4 The Epigenome 627 Chapter 22 Developmental Genetics and lmmunogenetics 633 The Origin of Spineless Sticklebacks 633 22.1 Development Takes Place Through Cell Determination 634 Cloning Experiments on Plants 635 Cloning E"periments on Animals 635 22.2 Pattern Formation in Drosophila Serves As a Model for the Genetic Control of Development 636 The Development of the Fruit Fly 636 Egg-Polarity Genes 637 Segmentation Genes 640 Hon1eotk Genes in Drosopllila 640 Hon1eobox. CJtnes in Other Organisn 1s 642 CONNECTING CONCEPTS The Control Of Developm ent 643 Epigenetic Changes in Development 643 22.3 Genes Control the Development of Flowers in Plants 644 Flo Ver Anaton1y 644 Genetic CAmtrol of Flower Development 644 CONNECTING CONCEPTS Comparison of Development in Drosophila and Flowers 646 22.4 Programmed Cell Death Is an Integral Part of Development 646 22.5 The Study of Development Reveals Patterns and Processes of Evolution 647

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22.6 The Development of Immunity Is Through Genetic Rearrangement 649 The Organizatfon of the ln1 n1uneSysten1 650 Jmmunoglobulin Structure 651 The Generation of Antibody Diversity 652 T· Cell· Receptor Diveraity 653 Major Histocompatibility Complex Genes 654 Cnes and Organ Transplants 654 Chapter 23 Cancer Genetics 661 Palladin and the Spread of Cancer 661 23.1 Cancer Is a Group of Diseases Characterized by Cell Proliferation 662 Tu n1or Forn1ation 662 C..ancer As a Genetk Di.ease 663 The Role of Environn1ental Factors in Cancer 665 23.2 Mutations in a Number of Different Types of Genes Contribute to Cancer 666 Oncogenes and Tumor-Suppressor Genes 666 Mutations in Genes That Control the Cycle of Cell Division 668 DNA-Repair Genes 672 Cnes That RegLtlateTelomerase 672 Cienes That Pmn1 ote Vaculariz.ation and t he Spread ofTumors 672 lvlicroRNAs and Cancer 673 Cmcer Genome Projects 674 23.3 Epigenetic Changes Are Often Associated with Cancer 674 23.4 Colorectal Cancer Arises Through the Sequential Mutation of a Number of Genes 675 23.5 Changes in Chromosome Number and Structure Are Often Associated with Cancer 676 23.6 Viruses Are Associated with Some Cancers 678 Chapter 24 Quantitative Genetics 683 Corn Oil and Quantitative Genetics 683 24. 1 Quantitative Characteristics Vary Continuously and Many Are Influenced by Alleles at Multiple loci 684 The Relation Between Genotype and Phenotype 684 Types of Quantitative Characteristics 686 Polygenic Inheritance 686 Kernel Color in Wheat 687 Detern 1ining Gene Nun1ber for a Polygenic Characteristk 688 Contents xiii 24.2 Statistical Methods Are Required for Analyzing Quantitative Characteristics 689 Distributions 689 Samples and Populations 690 The Mean 690 The Variance and Standard Deviation 691 Correlation 692 Regression 693 ApplyingStatistks to the Study of a Polygenk Characteristk 695 24.3 Heritability Is Used to Estimate the Proportion of Variation in a Trait That Is Genetic 696 Phenotypic Variance 696 Types of Heritability 698 Caln tlating Heritability 698 The Limitations of Heritability 700 Locating Gen es That Affect Quantitative Characteristks 702 24.4 Genetically Variable Traits Change in Response to Selection 704 Predkting the Response to Selection 705 Limit to Selection Response 706 Correlated Responses 707 Chapter 25 Population Genetics 715 Genetic Rescue of Bighorn Sheep 715 25.1 Genotypic and Allelic Frequencies Are Used to Describe the Gene Pool of a Population 716 Calculating C.enotypic Frequencies 717 Calculating Allelk Frequencies 717 25.2 The Hardy- Weinberg law Describes the Effect of Reproduction on Genotypic and Allelic Frequencies 719 Genotypic Frequencies at Hardy- Weinberg Equilibrium 719 Closer Exan1ination of the Hardy- Weinberg Law 720 Implications of the Hardy- Weinberg Law 720 Extensions of the Hardy- Weinberg Law 721 Testing for Hardy- Weinberg Proportions 721 Estin1 ating Allelic Frequencies \\1ith the Hardy- Weinberg Law 722 25.3 Nonrandom Mating Affects the Genotypic Frequencies of a Population 723

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xiv C ontents 25.4 Several Evolutionary Forces Potentially Cause Changes in Allelic Frequencies 726 Mutation 726 Migration 727 Genetic Dri 728 Natu ral Selection 731 CONNECTING CON CEPTS The General Effects of Forces That Change Allelic. Frequencies 736 Chapter 26 Evolutionary Genetics 743 Taster Genes in Spitting Apes 743 26.1 Evolution Occurs Through Genetic Change Within Populations 744 26.2 Many Natural Populations Contain High levels of Genetic Variation 745 Molecular Variation 745 Protein Variation 7 46 DNA Sequenc Variation 747 26.3 New Species Arise Through the Evolution of Reproductive Isolation 749 The Biological Species Concept 749 Reproductive Isolating Mechanisms 750 Modes of Speciation 751 Genetk Differentiation Associated \-.rith Speciation 755 26.4 The Evolutionary History of a Group of Organisms Can Be Reconstructed by Studying Changes in Homologous Characteristics 756 The Alignment of Homologous Sequences 75 7 The Construction of Phylogenetic Trees 758 26.5 Patterns of Evolution Are Revealed by Molecular Changes 758 Rates of Molecu lar Evolution 759 The Molecular Clock 760 Evolution Through Changes in Gene Regulation 761 Genon1e Evolution 762 Reference Guide to Model Genetic Organisms A 1 The Fruit Fly Drosophilia melauogaster A2 The Bacteriun1 F.scherichia coli A4 The l\1en1atode \•Vorn1 Ole11orhabditis elegans A6 The Plant Aralidopsis t/Ja/iaua AS The Mouse 1 \ifus tnusculus A 10 The Yeast Saccharo1nyce.s c.erevisiae A 12 Glossary s1 Answers to Selected Questions and Problems c1 Index 0 1

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1 Introduction to Genetics Albinism in the Hopis Rising a th ousand fl.et above the desert floor Black Mesa dominates the horizon o f the Enchanted Desert and provides a fan1iliar landn1ark for travelers pas.sing through northeastern Ariz. ona. Not only is B lack lvesa a pron1inent geological feature but n1oresignificantlr it is the ancestral h onle of the Hopi Native An1ericans. Fingers of the n1esa reach out lnto the desert and alongside or on top of each finger is a Hopi village. Most of the viU ages are quite small having only a few do· zen inhabitants but th ey are incredibly old. One viU age Oraibi has existed on Black Mesa since J ISO A.O. and the oldest continuously occupied settlen1ent in North An1erica. In J 900 Ales Hrrllika an anthropologist and physician \forking for t he An1erican fuseun1 of Natural History visited the Hopi viU ages of Black ·esa and reported a startling discovery. An1ong t he Hopis \/ere 11 \Y"hite persons- not Caucasians. but actually \Yhite Hopi Natlve An1ericans. These persons had a genetic condition knom as albinisn 1 Figure 1. 1. A Hopi pueblo on Black M e-sa. Albinism a genetic condition arises v.ith high frequency among lhe Hopi people and occupies a special place in the Hopi culture. Ansel Adams/Nat«ncll Pad: Atch\ es at Coilege P ari: MD.I Albinisn1 is caused by a defect in one of the enz.yn1es required to produce n1elanin the pign1ent t hat darkens our skin hair and eyes. People \lith albinisn1 either dont produce n1elanin or produce only sn1all an10unts of it and consequently have \lhite hair light skin and no pign1ent in the irises of their eyes. Melanin normally protects the D NA of skin celL i fro n1 the dan1aging effect.i of ultraviolet radiation in sunlight and n1elanins presenc. e in the developing eye is essential for proper eyesight. The genetic basLs of albinism was first described by t he English physician Arch ibald Garrod \/ho recognized in 1908 that the c.ondition .as inherited as an autoson1al recessive trait n1eaning t hat a person n1ust receive t.o copies of an albino n1utation­ one fron1 e-ach parent- to h ave albinis1n . In recent years the n1olecular natures of th e n1utations that le-ad to albinisn1 h ave been elucidated. Albinisn 1 in hun1ans is caus«l by defects in any one of several d ifferent genes t hat control the synthesis and storage of n1elanin n1any different types of n1utations can occur at each gene any one of "hk h n1ay lead to albinisn1. The forn1 of albini.sn1 found in the Hopis is n1ost Likely oculocutaneous albinlsm albinlsm affecting t he eyes and skin type Jl due to a d efect in the OCA2 gene on ch ron1oson1e J 5. The Hopis are not unique in baving albino.i an1ong t he n1en1bers of t heir tribe. Albinisn 1 i.i found in aln10.st all bun1an ethnic groups and li d escribed in ancient \\Tri tings 1

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2 CHAP T ER 1 1.1 Albinism among the Hopi Native AmeriC U \S. In this photograph taken .around 1900 the Hopi girl in the center has albinisnl. The Museum.ChariesCa rpe1ter .I it has probably been present since hun1ankindS beginnings. \..Yhat is unique about the Hopti is the high frequency of albinisrn in their population. In n1 ost hun1an groups aJbinisn1 i.c rare present in only about J in 20000 persons. Jn the villages on Black lvfesa. it reaches a frequency of l in 200 a hundred tin1es as frequent as in n1ost other populations. " hy is albinisn1 so frequ ent an1ong the Hopis The ans.er to thi.c question is not con1 pletely knom but geneticists \/ho have studied a lbinisn1 in the Hopi.s speculate that the high frequency of the albino gene related to the special place that albinism occupied in the Hopi cultu re. For n1uch of their history the Hopis considered n1en 1bers of their tribe \Ii.th albinisn1 to be in1portant and special. People \rith albinisn1 \/ere considered pretty clean and intelligent. Having a nun1ber of people \Yith albinisn1 in oneS village was co nsid ered a good sign a symbol that the people of the village contained partk ularly pure Hopi blood. Albinos performed in Hopi ceremonies an d held positions of leadership \\1ithin the tribe often as chiefi healers and religious leaders. Hopi albinos \1ere also given special treatn1 ent in everyday activities. The Hopti have formed small garden plot at the foot of Black Mesa fur centnries. Every day cluoughout the growing season th e men of the tribe trekked to th e base of Black Mesa and spent n1uch of the d3r in the bright south\/estern sunlight ten ding their corn and vegetables. \t\ lth little or n o n1 elanin pignlent in their skin people "ith albnisn1 are extren1ely susceptible to sunburn and have increased incidences of skin cancer "hen e.xposed to the sun. Furthern 1ore n1any dont see .eu in bright sunlight. Therefore the n1ale Hopis .th albinisn1 \¥ere excused fron1 this norn1al n1ale labor and allo.ed to ren1ain behind in the village \Yith the "on 1en of th e tribe perl0rn1ing other duties. Throughout the gro\Ying season the albino n1en "ere the only n1ale n1en 1bers of the tribe in the village with the women during the day and thus they enjoyed a mating advantage which helped to spread their albino genes. Jn addition the special considerations given to albino Hopi.c aUo.ed then 1 to avoid the detrixr1ental effects of albinisn1- increased skin cancer and poor eyesight. The sn1all si1.e of the Hopi tribe probably also played a role by allowing chance to increase the frequ ency of the albino gene. Regardles- of the factors that led to the h igh frequency of albinism the Hopis clearly respected and valued the n1en 1bers of their tribe "ho possessed this particular trait. Unfortunatel y people "ith genetic conditions in n1any societies are often subject to discrin 1ination and prejudke. TRY PROBLEMS 1 ANO 25 G enetics is one of the n1ost rapidly advancing field i of science "ith in1portant ne" di.icoveries reported every n1onth. Look at al n1ost any n1ajor ne\Y.spaper or ne..s n1agazine and chances are that you \1ill see artkles related to genetk.s: the con1pletion of another genon1e su ch as that of the Monarc. h butterfly the d i.icovery of genes that affect n1ajor diseases including n1ultiple sclerosLi depression and cancer a report of DNA anal y1..ed fron1 long-extinct anin1 a.Li such as th e \lfOolly n1an1n1 othi and the identifica· tion of genes that affect skin pigmentation height and learning ability in hun1ans. Even runong advertisen1ents you are likely to see ads for genetic testing to detern 1ine a per.sons ancestry paternity and .susceptibility to diseases and disord ers. These ne\\1 findings and applkation.s of genetics often h ave .significant econon1ic and ethical irnpli· cations n1aking th e study of genetics relevant tin1 ely and interesting. biology course. \t\e begin by considering the in1portance of genetics to each of us to society at large and to students of biology. We then turn to the history of genetics how the field as a whole developed. The final part of the chapter presents .son1e fu ndan1ental ternlS and principles of genetics that are used th mughout the book. 1 .1 Genetics Is Important to Us Individually to Society and to the Study of Biology Albinlin1 an1ong the Hopti illustrates th e in1 p ortant role that genes play in our lives. This one genetic defect an 1ong the 20000 genes that humans po-°ss completely changes the life of a Hopi \\fho possesses it. lt alters his or her occupation. role in Hopi society and relations "ith other n1en 1bersof the tribe. \"le au possess genes that influence our lives in signifi· cant \\Tays. Genes atfect our height \/eight hair color and This chapter introduces you to genetk.s and reviev.s son 1e concepts that you n1ay have encountered briefly in a

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a b Chromosome S 1.2 Gene-s Influence susceptibility to many dl.sease-s and disorders. a An X·tat of the hand of a person sufferin9 from diastrophic dysplasia bottom a hereditary grovtth dlsorder lhat results in cutved bones short limbs and hand deformities compared with an X· 1 21f of a normal hind top. b This disorder is due toa def ea in the SlC26A2 gene on c.hrom:£ome 5. Pan a: topS::ophoto Asso:JateSISaence SourooPhoto Researchers bottcm from Johama Htistbad:a et .. Cell 786 pp. 1073-1 087 1994. Cl 1994 E heviet. Courtesy of Prof. E ttc: Lander Whrtehead Institute . I skin pign1entation. They affect our susceptibility to n1any diseases and disorders Figure 1.2 and even contribute to our intelligence and personality. Genes are fundan1ental to .ho and \\hat .e are. Although the science of genetic.i is relatively De\/ c.on1· pared \\Tith sciences such as astronon1y and chen1istry peo· pie have understood the hereditary nature of traits and have practic- ed genetks for thousands of years. The rise ofagrkul· tur e began when people started to apply genetic principles to the don1estk ation of plants and anin1als. Today the n1ajor crops and anin1al.s used in agricultur e are quite dift irent fron1 their \\ild progenitors having undergone extensive genetic alterations that increase their yield.s and provide n1anr de.sir· able traits such as disease and pest resistance special nu .. tritional qualities and characterlotics that facilitate harvest. The Green Revolution \Vhich expanded food production throughout the world in the 1950s and 1960s relied heavily on the application of genetics Figure 1.3. Today genetically engineered corn soybeans and other crops constitute a sig .. nificant proportion of all the food produced worldwide. The pharn1aceutk al industry is another area in \Vhkh ge .. netic.s plays an in1portant role. Nun1erous drugs and food ad · ditives are synthesized by fungi and bacteria that have been genetically n1anipulated to n1ake then1 efficient producers of these substances. The biotechnology industry employs n1olecular genetic techniques to develop and n1ass-produce 1.3 In the Green Revolution. genetic te:hnlqoos were used to develop new hlgh..ylelding strains of crops. Left r-«rman Bodaug a leader in the development of new v.ltieties of \Yheat that led to the Green R evolution. Borlaug was av .. arded the Nobel P eace P rize in 1 970. R ighO Modern. high-yielding rice plant left and tradoional rte plantright. p.ett: BettmannlCOhs. Right: tRRl.I substances of con1n1ercial value. GRnvth horn1ones insu· lin clotting factor enz.yrne.i antibiotics vaccines and n1any drugs are now produced commercially by genetically engi· neered bacteria and other cells Figure 1.4. Genetics has also been used to produce bacteria that ren1ove n1inerals fron1 ore break do\/n toxic chen1icals and inhibit dan1aging frost forn1ation on crop plants. Gnetics also plays a critkal role in n1edicine. Phskians rec. ogniz.e that n1any diseases and disorders have a hereditary con1ponent including rare genetk disorders such as skke .. cell anen1ia and Huntington disease as \V ell as n1any con1 .. n1on dis . eases such as asthn1a diabetes and hypertension. Advances in genetics have resulted in in1portant insig hts into the nature of d iseases such as cancer and in the developn1ent of diagnostic tests including those that identify pathogens 1.4 The biotechnology Industry uses moleul:ir genetic methods to produce substances of economic value. V\ndre\\• Soo\:eYCotbis.I 3

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4 CHAPTER I and defectne genes. Gene therapy-the d1tCt altenulon of g.enu to tre11 human diseases-has now hem adminltered 10 thOU.lnd of patients although 115use1utU txpmmenal and limited 10 treating a few disorders. The Role of Genetics in Biology All hough an understanding of genetics 1 lmpt.lrton l to 1111 pcoplc his crilical to 1he S1t1denl of biology. Clcnctlcs pm vidl: one of biologys unifying prin dplcs: 1111 orgnnism• use genetic systen 1io that have a nun1ber of fuuturt ln ron1n1on. C:t1"11lcs ol:o undergirds the study of mnny other biological didplines Evolution for example ls genetic chMgc toking plae through time so the study of e\llution rcquins an un­ dersc on ding of genetics. Devdopmental biolo8J1 rdlls heavily on gmetk: tu.sues and orgmsd..-elop through the regulated uprestlon ol genes Figure 1.5. fa-en iuch field as tuono· mi-. ecology. and animal beha»10r are makmg Increasing use of genetic methods. The 111uly of almal any fidd of bl deg or medicine is incomplete without a thaougb underlanding o goi-es and genetic methods. Genetic Diversity and Evolution Life on F.orth exisrs in a tremendous arruy of ltitn1 11ncl fea­ turci in uln1ost every conceivable environn1cnt. Life lJ :1lso cht1racterl7.cd by adaptation: many organisms It cxqulitely suited 10 the environment in whkh they ore iunl.1he h i· tory of life i• a dtromde of new forms of hfe emerging old faros dbappeanng and existing imu hanging. Despite their ucmendous dive...ty living Ot8"nlms have 1n lmportmt feature m ccrnmon: ii use .s1mU11r genttK: -s· terns A complete set of genetic insUUbotU ir an organ· lllll Is it genome and all genomes are mcoded In nudek •cids-enher DA or RNA. 1he coding Sfl111 for genomic 1nfom1anon is also common to aU life: gencuc tnstruaions are in the same format and. with rare txccpUons lhc code words are identical Likewise. the pmce.s.s by which genetk 1. The key todevelopmtnt Des In the uladon of gene upreulon. TIUs....tyfn.11-fly tmlXO•"ll"-OS 1MIOU "4ft...al of tllto Mgrililed gene. v.l.dl he\ Hli... " __ ol booy S19ments in Ille adol ny. I_ Po_ I information is copied and docodcd lo rtlllarl:ably similar fa all irms of life.. 1hese commM features of heredity suggest tha all life on Eo.rth e\-Olvod fmm the same primordial an· cestor that arose between 3.5 blDion and 4 bilHoo years ago. 81ologi.st Richard Dawkins d0aibes hk -as a rl\er of DNA thm runs through lime ronnectlng all organisms past and present. Thm a u organism h ave ilmilnr senetic sy1ems mean.• that the siudy of one orgnnlsms SllCS reveal: principles that apply to other orgunisnts. Jnvctig:ttion o ho" bacterial DNA is copied replicOled for cxomrlc provide informa· tion that applies to the Rplicotlon of humon DNA. lt alo mea11-• that genes will function in foreign cells which makes genetic engineering pos.sibk. Unforiunateiy these similar genetic systerru are also the basis lot d1 such as Al DS acqnired immune deficim: syndr. m which viral genes are able to functlon- 001C11tnes with alarming efficiency-in human cdt. Lifes dnlmty and •d•plllllon are products of "lliulion which is sin1ply genetic changl through lime. Evolution is a two-step proc.s: firs tnhcriled d1flercna:s anse randomly and then the proportion or 1ndMduals " i th partw:ular dif­ ferenceSincreases or dectta.ses. Genedc variation is therefore tbe foundation of all evolulionury change and l u ltima1ely th e basis of all life as "e kntJ\\t It. Furthcrn1ore techniques of n1olec.u1ar genetks 11rc nO\I routinely used to decipher evolutionary relationships lunang organisn1 s for exaniple recent analvsls of DNA isoln1cd from Neondertbal fossils has yielded new in formatiM concerning the relationship bet\oeen Neanderthals and rnodem hunians. demonstrat· ing that Ne-anderthals •nd the ancestor o modem romans likelr interbred some 30000 tn 40000 y•ars ago. C.enetics the study ol genebc •-:ui31.lon ls crlftcal to understanding the past present and uturt olllft. TllY PllOBLEM 17 CONCEPTS He-redity affects many of our physic.al features as well as our susceptibility to many dise3SCS and d isorders. Genetics con· tributes to advances In agrlulturl pharmaceutica Is • • ind medicine: and is fundamonUll to modern biology. All organ· isms use s imilar genetic systems and gene. tic vati ation is .the foundat ion of the dlwrslty of all Ille. Y CONCEPT CHECK 1 \M\al dte SOfl"le of l™" .-npltGtlOn\ of al OUatUSms. h.a8ng Slmiar geneocsystm17 •· That all ii fotrru "9flllt1aty 1e1110 b That Ch findingson-Ot"" gmelunClman often be •ppild .. othr Oftl•nr.tnS c. 1h1l gmes from onnlm QIO o/IM •MS .00thn...11 anotfef Ofgarusm d. Al ol lheallove

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Divisions of Genetics The study of genetics oonslsts of 1hrtt major subdisdplines: transmisslon geneticS- n1olecular genetics and population genetics Figutt I.AS . Also known as da.sical genetics transmission genetics enconlp3S-SCs the baste principles of hereditandhow traits attpassed from one generation tot he next. This area addresses the relation bc_.t\·een c.hr001osomes and heredilI the arrangement of genes on chromosomes and gene mappng. Here the focus is on the mdMdual organism- ho\\ an tndiVidual orgmusm inherits its genetic makeup and how it passes its genes to the next generation. Molecular genetics concerns the chemical nature of the gene itself: how genetic information Is encoded replicated and expressed. It includes the ceUuLtr processes of replica· tion transcription and translation by which genetic inir· mation is transferred from one molecule to another and gene regulation the processes that control the expression of genetic infornu1tion. The focus in molecular genetics is the gene. its structure. organization. and function. Population genetics cxplor the genetic cornposition of groups of individuol members of the snme species popula· tion. and how that composition chonges geogrophically and \\1ith the passage oftin1c. Bccnusc evolution is genetic change Transmission Molecular genetics oenttic.s Populotlon geneucs 1.6 Genetic.scan be subdivided Into thrtt interrelated fields. llc:p I. kn:on B.ldirthve/A.my b p tiQtll MitrllI twke arthy/Getty tnages.. Bottom: Stwrt WOIVSOtftCll S I Introduction to Gene1ics 5 population genetics is fundamentall the siudrof evolution. The focus of population genetics is the group of genes found in a population. Division of the study of genetics into these thrtt groups is oonwnient and traditional but we should recognize that the fields aerlap and that each major subdMsian can be funher dMded into a number of more-specialized fields. such as chromoscmal genetics.. biochemical genetics. "1anlitauvc ge netics and so forth. Alternati\-ely genetics can be subdividtd by organism fruit fly com. or baaerial genetics and ••ch of these organisms may be studied at the level of transmlS sion molecular and population genetics. Modern genetics is an extremely broad field encompassing many interrelated subdisciplines and specializations. TRY PROBLEM 18 Model Genetic Organisms Through the years genetic studies have been conducted on thousands of different species including almost all major groups of bncteria. fungi. protists. plants and anin1als. Nevertheless a fe\\1 species have en 1ergcd as ntcxlcl genetic organisms-organiin1s having characteri."tic.. chat n1akc them particularly LLful for genetic anotysis ond obout which a tren1endous an1ount of genetic inforn1ation h:.1s t\ccun1u· lated. Six model organism that have been the subject of in ­ tensive genetic study are: Dro.sophiln 111cln11ogns1er n f rult flyi Escherichia coli a bacteriun1 present in the gut of hun1:\ns and other n1an1n1alco Ole11orhabditis elegn11s a ncn1atodc \/Orn1: Arnbidopsis thaliaua the th ale· cre....s plant 1\ifus u1ululus the bouse mousej and Saaharo1nyces cerevisiae bakers rcast Figutt 1.7. These species are the oigan lms of choice for n1any genetk researchers and their genon1es \Vere sequenced as a part of the Human Genome Projea s.. Chaplet 20. The lik cytes and genetic characteristics of these model genetic organisms are described in n1ore detail in the Rcftrence Guide to Model Genetic Organisms located at the end of this book pp. Al - Al3. This Rekrence C.uide wil l be a useful resource as you encoonter these organisn1s througho.n tht book. At first glance this group of lowly and some111nes unap p-eciated creatures might seem unlikelrcandidates for mod el organisms. Howe\-er all posse" life crcles and traits that make them particularly suitable for genetic study. 1nduding a shon generation time large but manag .. ble numbers of p-ogeny adaptability to a laboratory environment and th• ability to be housed and propagated inexpensh·ely. Other species that are frequently the subjects of genetic research and considered genetic n1odels include f\eurospora c:rassa bread mold Zea mays corn Da11io rerio zebrafish and Xwopus /aevis clawed frog. Although not generally con· sidered a genetic model. hun1ans al have been subjected to intensive genetic scn1 tinyospecial techniques for the genetic analysisofhumansare d iscussed in Choptcr6.

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6 CHAPTER I a b Drosophila melonogaster Fruit fly pp. A2-A3 cl Coenorhabdil is elegons Nematode pp. A6-A7 1.7 Model genetic organisms c:ire species with features that make them useful for genetic analysis. Palla: SPtJPhoto ResearchetS. Part b: Pas:iekaPhoto Researchers Inc. Patt c: SWtda .. Stammm/Photo R.eseatchets inc. Pan d: Peggy Gr d/AAS USDA. flan e: Joel Page/AP. Pan f: SXlphoto rusocatPfKto R.esearche-rs .I The value of n1odel genetic organisn1s i.s illustrated by the use of zebrafish to identify genes that affect skin pigmen· talion in hun1ans. For n1any ears geneticiots have recog· niz.ed that differences in pign1entation an1ong hun1an ethnk groups are genetk Figure l.8a but the genes causing these differences \/ere largely unkno""· The zebrafish has becon1e an in1portant n1odel in genetic studies because it is a sn-lall vertebrate that produces n1any offspring and is easy to rear in the laboratory. The mutant zebrafish called goldrn has light pign1entation due to the presence of fe\ler sn1aller and les..i· dense pign1ent· containing structures called n1elanoson1es in itscells figure l.8b. Keith Cheng and h i colleagues hpothesized that light skin in hun1ans n1ight result fmn1 a n1utation that is sin 1i .. lar to the golde11 mutation in zebrafish. Taking advantage of the ease ""ith "hkh z.ebrafish can be n1anipulated in the laboratory they isolated and sequenced the gene respon· sible for the golden n1utation and found that it encodes a a b Normal zcbrafish protein that takes part in calciun1 uptake by n1el anoson1es. They then searched a database of all kno\.n hun1an genes and found a similar gene called SLC24A5 which encodes the san1e function in hun1an celL i. \+Vhen theyexan1ined hun1an populations they found that light-skinned Europeans pi· cally possess one forn1 of this gene \\1hereas darker·skinned Afrkan..i Eastern Asians. and Native An1ericans u.suallr pos· sess a different form of the gene . . Man other genes alo affect pign1entation in hun1ans as illustrated by n1utations in the OCA2 gene that produce albinisn1 an1ong the Hopi Native An1ericans discussed in the introduction to this chapter. Nevertheless SLC24A5 appears to be responsible for 24 to 38 of the differences in pign1entatton beh.een . .l\frkansand Europeans. This exan1ple illlLitrates the po\1er of n1odel or .. ganisn1s in genetk research. Ho\\lever "e should not forget that all organisn1s poss . ess unique characterlotics and son1e­ tin1es the genetic -. of n1odels do not accurately reflect the ge­ netic systen1s of other organl-.n1s. Colden 1 nutant 1.8 The zebraflsh a model genetic organism has been Instrumental in helping to Identify gene-s encoding pigmentation differences among humans. a Human ethnic 9roups differ in degree of skin pigmentation. b The 2ebrafish golden mutation 6 c.aused by a gene that controls lhe amount of melanin pigmenl in melanosone.s. IPan a: flhotoDisdGeny mages. Part b: Kerth ChmgJat:e Gnden. CalIC.ef Researdl fot.rdatron Pennsytvania State Coiege of MedOne.I

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lntrod uaion to Genetics 7 d e fl Mus musculus Arabidopsis choliono Thalc·crcss plant pp. A8-A9l House mouse pp. A I 0-A 11 SacchaYomyces ceYevisiae Bakcr"s yeast pp. A 12-A 13 CONCEPTS The thre-e major divis ions o f genetics are transmission genet· ics. molea..ilar genetics and population genetics. T ransmission genetics examines the principles of heredity molecular genet· ics deals with the gene and the cellular processes by w hich genetic information is transferred and expressed population genetics concerns the genetic composition of groups o f organ· isms and how that compos ition changes geographically and w ith the pas.sage of t ime. Model genetic organisms are species that have received special emphasis in genetic research they have characteristics that make them useful for genetic analysis . V CONCEPT CHECK 2 woo Id the hO"Se make a 9QOd model genetic organism Wtrf or\\hy not 1.2 Humans Have Been Using Genetics for Thousands of Years Although the science of genetics is young- aln1ost entirely a product of the past J 00 years or so- people h ave been using genetic principles fur thousands of yea". The Early Use and Understanding of Heredity The 6rst evidence that people understood and applied the principles of heredity in earlier tin1es is found in the do · n1estication of plants and anin1 als \\lhk h began beh\Teen approximately 10000 and 12000 years ago in the Middle East The first don1esticated organisn1s included \/heat peas lentils barley do gs goats and sheep Figure l .9a. By 4000 rears ago sophisticated genetic techniques \Y-ere already in use in the Middle East. The Assyrians and Babylonians developed several hundred varieties of date paln1s that differed in fruit siz.e color taste and tinle of ripening Figure l.9b. Other crops and dom esticated ani· nlals \Y-ere developed by cultures in .sia .frica and the An1ericas in th e san1e period. Ancient \Vritings den1onstrate that earl hun1ans \tere also a\.ra. re of their O\in heredity. Hindu sacred \\lritings dat .. ing to 2000 years ago attribute nlany traits to the father and suggest that differences bet\teen siblings are produced b the mother. The Talmud the Jewish bookofreligioLc laws based on oral traditions dating back thou.sandi of years presents 1.9 Ancient people-s practiced genetic technlque-s In agrlc"Ulture. a Modem ·heat v1ith larger aod more nunlercus seeds that do not scaner before hai\est \"•as produced by interbreeding at leas:t lhree daterent ·ild species. b As.syrian bastelief sculpture show1n9 artJfkial poUinauon of date palms at the time of King Assurnasirpalli II who reigned from 883 10859 a.c. Pan a: Scou SaJg/ARSAJSDA. Panb: La.wt r e96te1: knage-copfgltCI The uopoitanMuseum of Art. knagesotXce: Art ResotXce NY.I

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8 CHAPTER I an uncannily accurate understanding of the inheritance of hen1ophilia. Jt directs that if a \von1an bears t\/o sons .ho die of bleeding after circun1cision any additional sons that she bears should not be circun1cisedi nor should the sons of her sisters be circun1cised. This advice accurately corre· sponds to the X-linked pattern of inheritance of hemophilia di.cussed further in Chapter 6. The ancnt Greeks gave careful consideration to hun1an reproduction and heredity. Greek philosophers developed the concept of pangenesis in .hich specific particles later called gen1n1ules carry inforn1ation fron1 various parts of the body to the reproductive organs fron1 \lhich the are pass- ed to the embryo at the moment of conception Figure I.JO. Although incorrect the concept of pangenesis \\13.i highl in· fluential and persited until the late I SOOs. Pangenesis led the ancient Greeks to propose the notion of the inheritance of acquired c. haracteristics in \/hkh traits acquired in a persons lifetin1 e becon1e incorporated into that persons hereditary in forn1ation and are pass- ed on to offapring for example people who developed musi· cal ability through diligent study would produce children "ho are innately endo\Ved \oJith n1usica1 ability. The notion of the inheritance of acquired characteristks i.i also no Ion .. ger accepted but it ren1ained popular through the t\oJentieth c. entury. Although the ancient Ron1ans c. ontributed little to an understanding of hum an heredity they successfu lly devel· oped a nun1ber of techn iques for anin1a1 and plant breed .. ing the techniques \/ere based on trial and error rather than any general concept of heredity. Little ne\/ inforn1a · tion \oJas added to the understand ing of genetics in the next JOOO years. Ad ditional developn1ents in our understanding of he· redity occurred during the seventeenth century. Dutch eyeglass nlakers began to put together sin1 ple nlicroscopes in the late I SOOs enabling Robert Hooke 1635- 1703 to discover cells in 1665. vfkroscopes provided naturalists \oJith ne\/ and exciting vistas on life and perhaps exces .. sive enthu.siasn1 for this ne\I/ \/orld of the very sn1all gave rise to the idea of preforn1ationisn1. According to pre .. forn1ationisn1 inside the egg or spern1 there exists a fully forn1ed nlin iature adult a ho1nunculus "hich sin1ply en· larges in the course of development Figure 1.11. Prefor· niationisn1 nleant that au traits \/ere inherited fron1 only one parent- fron1 the father if the hon1unculus \I/as in the spern1 or fron1 the nlother if it " as in the egg . . A.lthough nlany observations suggested that offipring pos..i-ess a nli.x .. tu re of traits fron1 both parents preforn1ationisn1 ren1ained a popularcone-ept throughout nluch of the seventeenth and eighteenth centuries. a Pangenesis concept b Germ-plasm theory According to the pan9enesis concept 9ene-tic information f ronl different parts of the body ..• ... lfNels to the o zvgote Accordin9 to the germ-plasm theory. germ..iine tissue in the reproductive Of9lns .. ... contains a conplete set of 9ne-tic information ... . that iS uans:ferted 1tect1yto the game-Les . .. /Sperm Egg . Zygote 1.10 Plnge.nesis In early concept of inheritance compared with the modern germ-plasm theory.

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1.11 Preformationi.sts in t he seventeenth and eighteenth centuries believed that sperm or eggs contained fully folmed humans the homunculus. Shov.•n here isadra iuin9 of a homuncuJus ins.Kie as.perm. 5oence Sour ce.I An other early notion of her edit \\las blendiJ1g i11herita1K.e. whk h proposed that offspring are a blend or mixture of pa· rental traits. Thls kiea suggested that the genetic n1aterlal it· self blends. much as blue and yellow pigments blend to make green paint. After having been blended genetic differences could not be separated in future generations. just as green paint cannot be separated into blue and yello\\I pign1enc.s. Son1e traits do appear to exhibit blend ing: inheritance ho\. .. ever "e realtz.e today that indivKiual genes do not blend. The Rise of the Science of Genetics In 1676 Nehemiah Grew 1 641- 1712 reported that plants reproduce sexually by using pollen from the male sex cells. \\Tith thii infurn1ation. a nun1berofbotanists began to experi· n1 ent \\lith ems.sing plants and creating hybridi including Gregor Mendel 1822- 1884 Figure 1.12. who went on to dis· cover the bask principles of heredity. Mendell conclusions "h kh .ere not ..kfely kno\m in the scientific con1n1unity for 35yean laid the foundation for our modern understanding of heredity and he is generally recognized today as the father of genetks. Developments in cytology the study of cells in the 1800s had a strong influence on genetics. Robert Bro\m 1773- 1858 described the cell nucleus in 1833. Building on the work of others lvatthias Jacob Schleiden 1804- 1881 and Theodor Schwann 1810- 1882 proposed the concept of the cell theo ry in 1839. According to this theory all life is com· posed of cell s cells arise only from preexisting cells and the lntroduaion to Genetics 9 ceU is the fundan1ental unit of structure and fu nctton in living organisn1s. Biologists interested in heredity began to e.xan1ine cells to see \\lhat took place in the course of cell repmduc· tion. Walther Flemming 1843- 1905 observed the division of chromosomes in 1879 and published a superb description of mitosis. By 1885 biologists generally recognized that the nucleus contained the hereditary inforn1ation. Charles Darwin 1809- 182. one of the most influential biologists of the nineteenth century put forth the theory of evolution through natural selection and published his ideas in 011 the Origi11 of Species in 1 859. Darwin recognrted that heredity \1as fundan1ental to evolution and he conducted extensive genetic crosses "ith pigeons and other organisn1s. Hm .... ·ever he never understood the nature of inheritance and this lack of understand ing \\las a n1ajor on1ission in his theory of evolution. In the last half of the nineteenth century C1ologists den1onstrated that the nucleus had a role in fertilization. Near the close of the nineteenth centurr Aug ust \leis· mann 1834- 1914 finally laid to rest the notion of the in· heritance of acquired characteristks. He cut off the tails of n1ice for 22 consecutive generations and sh o\\led that the tail length in descendants remained stubbornly long. Weismann proposed the germ· plasm theory. whk h holds that the c. ell.s in the reproductive organs carry a c-0n1plete set of genetk inforn1ation that is passed to the egg and sperm see Figure J.J O b. 1.12 Gregor Mendel w as the father of modern genetics. Mendel first discover« the principles of heredity by crossin9 different \0rieties of pea plants and analyzjn9 the transmission of ttaits in subsequent generations.. HultM ArdrNGettytnages.I

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10 CHAPTER 1 lhe ye.or 1900 was a watershed in the history£ genellCs. Gregor Mendels pivotal 1866 publication on expenments "1th pea plants. which n\•ealed the principles of heredny wu redtsco•oered as considered in more detail in Chapter 3. lhe significance of his conclusions \\".lS recognized. and other biologists immediately began to conduct similar ge­ netic studies on n1ice chkken.... and other orgonbms. The rults of these investigations stio\Yed th:u n1any traits indeed follow Mende ls rules. Some of the early concept• of heredity re sun1n1arized in Table 1.1. Aer the acceptance of Mendels theory of heredity. in 1902 Walter Sutton 1Sn- 1916 propos..cod that genes the units of inheritance are located on chron1oson1cs. lhon1as Hunt Morgan 1866- 1945 d iscovered the Arst genetic mutant of fruit flies in 1910 and used fruit 01es to unrav· el many druds of transmission genetics. Ronald A. FtSher 1890 1962 John B. S. Haldane 1892- 1964 and Sewall Wngh1 1889- 1988 bid the foundation for populotion ge· nehcs in the I 930s by integrating Mendebon g•nellCs and C\-Olulionary theory. Geneticbls began 10 use bacteria and viruses in the 1940s the rapid reproduction and simple genetic systems of these organisms allowed detailed study of the organiz.tion and structure of genes. At about this san1e tin1e evidence accu· n1ulated that DNA \\fas the repositoryofgcnetic inforn1ntion. Early concepts of heredit Concept lnhertance of lQUWed charactenst1cs Prcformaton1sm Blnd1ng U\hernce Genn-plasm t hooiy Cel theoy Mtndohan llllKirltance Proposed Genetic: tnfmaton trawfs from cflferent partsofthe body to repoduct.. 0gans. Ac:qu .. ed traits become incorporated into heted1taiy 1nonnation. Miniature organism resides 10 sex cells. and all traits are inherited from one parent. Genes blend and mix. All eels con.tan a c004llete set of geneoc: l"lfonnat1 00.. All Ile 6 composed oi Celt. and Celt aroe only from eels. Tra1t.s ate inherited in accord with defined praoc1ples. Corr0t or lntorr0t 1nc ouect 1ncor1tCt lOflQCt incorrnct Correa Coriea Correa CAGAGGAGCATCa: O:C:-CC• GO -:OCCTCTTGCxC JO 4 • •6 170 GlCACCl\AGOCCCAI:l\CCTCCACTCTOCJ\CACOTAOATGCTG 250 260 70 280 29 caCAcocoocccc- o c C oooo --ccrCllCC" 1.13 lhe hll"nan genome was completely sequenced in 2003. A chrana109raph ol • ..1 potbOO ol lhe human 90nome. ISoence MSPLI James Watson b. 1928 and Froncb Crick 1916-2004 along .th Maurice Wilkins 1916 2004 and Rosalind Franklin 1920- 1 958 descriled the thrtt dimeruional structure of DNA in 1953 ushering in the era of molecular genetics. By 16 the chemical structu re of DNA and the system by \1hich it detern1incs the 11nlino acid sequence of proteins had been \Vorked out. Advances in n1olecular genetics led to the first recon1binant ONA cxperin1ents in 1973 \¥hich touched off another revolution ln genetk research. VValter Gilbert b. 1932 and Frederick Sanger b. 1918 developed methods or sequencing DNA in 19n. The polymerase chain reaction. a technique or quiddy ampliflllg tiny amounts o DNA. was dt\-.loped by Kary MulJIS b. 1944 and others in 1983. In 1990. gene therapy was used for the first time to treat human genetic d1Seast In the IJmted States and the Human C.enorne Project w3s launched. By 1995 the first complete DNA sequence cl a free-livmg organism- the bac­ teriun1 Haenropl1ifus i11fluc11zac- \iilS determined and the first complete sequence of a cukaryotic: organisn1 yeast \fa.Iii reported a year later. A rough drnft of the human genome sequence was reported in 2000 stt Chapter 20 with the sequence es."ientially cornplctcd In 2003. ushering in a ne" era in genetic. Figurt 1.13. Today the genomes of nun1erous organisrns are being sequenced analyzed and compared. TRY PROBLEMS 22 AND 23 The Future of Genetics um«ous advanc.es in gme1tcs art being made today and ge· netics remains at the forefront or brnlogacal resean:h. \\ rapid methods for sequencing DNA are bang used to .._ quence the genomes of numerous spec1es from stta"ierries. to butterflies to elephant Recently. these methods were used to reconstruct the entire genome of 111 unborn fetus from i-tal DNA circulating in the mothers blood providing the poten· ti al for noninvasive prenatal genetic I sting. Analysis of DNA

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fron1 ancient bones den1onstrates that.several different species of hun1ans roon1ed the earth as recently as 30000 years ago. Po\/erfuJ n1odern genetk techniques are being used to identify genes that influence agriculturally in1portant characteristks such assize in cattle don1estic.ation in chicken.ispeed in race· horses and leaf shape in corn. DNA analysis is no\/ routinely used to identify and convkt crin1inaL i 1 or prove the innocence of suspecl. The pHler of ne\/ nlethods to identify and analyze genes is illustrated by genetk studies of nlyocardial infarction heart attack in hun1ans. Phrsicians have long recognized that heart attacks run in fan1ilies but fin ding specific genes that contribute to an increased risk of a heart attack h a.Ci until recently been difficult. In 2009 an international rean1 of ge· neticists exan1ined the DNA of 26000 people in JO countries for single nucleotide differences in the DNA called single· nu cleotide polymorphisms. or SNPs that might be associ· ated \\Tith an increased risk of heart attack. This study and other sin1ilar studies identified several ne\/ genes that affect the risk of c.oronary artery disease and early heart attacki. The.ie findings nlay nlake it possible to identify persons \/ho are predisposed to heart attack allo\ling early intervention that might prevent an attack. Analyses of SNPs are helping to locate genes that affect au trpes of traits fron1 eye color and height to glau con1a and cancer. lnforn1ation about sequence differences an1 ong organ· isn1s is also a source of ne\/ insights about evolution. For exan1ple scientists recently analyz.ed DNA sequ ences at 26 genes to c.onstruct a con1prehensive evolutionary tree of n1an1n1aLi. The tree uncovers nlany interesting features of n1an1n1alian evolution. One such revelation is that n1arine mammal whales dolphins and porpoises are most closely related to hippos. Jn recent years scientists have_ discovered that altera­ tions to DNA and chron1oson1e structure that do not in .. volve the base sequence of the DNA play an ilnportant role in gene expression. These alterations called epigenetic changes affect our appearance behavior and health and are currently the focus of intense research. Other studies den1onstrate that RNA is a key player in nlany aspects of gene function. The discovery in the late 1990s of tiny RNA nlolecules caU ed sn1all interfering RNAs and n1icro lNAs led to the recognition that these n1olecuJes play central roles in gene expression and developn1 ent. Ne\/ genetic n1icrochips thatsin1ultaneous ly analyze thousandi of RNA nlolecules are providing inforn1ation about the activities of thousands of genes in a given cell allowing a detailed picture of h o\. c. eU s respond to e.xternal signals environ n1 ental stresses and diseases such as cane.er. J n the field of proteon1ics po"erfu l con1pu ter progran1s are being used to n1 odel the structure and function of proteins fron1 DNA· sequence infOrn1ation. All of th li inforn1ation provides us "ith a better understanding of nun1erous biological pro· cesses and evolu tionary relationships. The flood of ne\\l genetic infOrn1ation requires the continuous d evelopn1ent lntroduaion to Genetics 11 of sophisticated con1puter progran1 s to store retrieve con1pare 1 and analyz. e genetk data and has given rise to the field of bioinformatics a merging of molecular biology and con1puter science. As the cost of sequencing becon1es nlore affordable the focus of DNA-sequencing efforc wiU shi from the ge· non1es of different species to individual differences \lith· in species. J n the not•too·distant future each person \\TiU likely possess a copy of his or her entire genon1e sequence \lhich c.an be used to help assess the risk of acquiring vari· ous diseases and to tailor their treatn1 ent should they arise. The use of genetks in agriculture \1111 continue to in1prove the productivity of don1estic crops and anin1 aL i helping to feed the future \iorld population. This ever .. \lidening scope of gen et ks raises significant ethical social and econon1ic is.su es. This brief overvie\/ of the history of genetics is not in­ tended to be con1 prehensive rather it is designed to provide a sense of the accelerating pace of advances in genetics. In the chapters to con1e "e "" learn nlore abo ut the experi· nients and the scientists .ho helped shape the dlicipline of genetks. CONCEPTS Humans first applied genetics to the domestication of plants and animals between 1 0000 and 12000 years ago. Develop" ments in plant hybridi zation and cytology in the eightnth and ninete-enth centuries laid the foundation for the field of genetics today. After Mendels work wa.s rediscovered in 1900 the science of genetics developed rapidly and today is one of the most active areas of science. .f CONCEPT CHEC K 3 How did devebpmenLS in cytology in the nineteenth cenLury conttit­ ute to our modern under.standing of genetics 1.3 A Few Fundamental Concepts Are Important for the Start of Our Journey into Genetics Undoubtedly you learned son1e genetic principles in other biology cl -asses. Lets take a fe\v n1 on1ents to revie\V son1e fun· dan1 entaJ genetic concepts. CELLS ARE OF TWO BASIC TYPES: EUKARYOTIC AND PROKARYOTIC Structurally cells conslt of two baic types althoug h evolutionarily the story i more complex see Chapter 2. Prokarrotic celL Ci lack a nuclear n1 en1brane and do not generally possess n1 en1brane-bounded cell organ· elles \1Jhereas eukaryotic cells are nlore con1plex poss.es.sing a nucleus and n1 en 1brane-bounded organelles such as chlo · roplasts and niitochondria.

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12 CHAPTER I THE GENE IS THE FUNDAMENTAL UNIT OF HEREDITY The precise ... -ay in \\Thk h a gene is defined often varies de· pending on the biological context. At t he sin 1plest level \\le can think of a gene as a unit of inforrnation that encodes a genetic characteristic. \\ 1 e \\fill expand this definition as \\le learn n1 ore abo ut \\lhat genes are and ho. they function. GENES COME IN MULTIPLE FORMS CALLED ALLELES A gene that specifies a characteristk n1ay exist in several forn1S called alleles. For e.xan1 ple a gene for coat color in cats n1 ar exist as an allele that encodes black fur or as an al· lele that encodes orange fur. GENES CONFER PHENOTYPES One of the m ost impor· tant concept in genetks is the distinction bet\/een traits and genes. Traits are not inherited directl y. Rather genes are inherited and along \Yith environn1ental factors detern1 ine the expression of traits. The genetic inforn1 ation that an in· dividual organisn1 possesses is its genotype the trait is its phenotype. For exan1ple albinisn1 seen in son1e Hopis is a phenotype and t he inforn1ation in OC.A2 genes that ca.us.es albinism is the genotype. GENETIC INFORMATION IS CARRIED IN DNA AND RNA Genetic inforn1ation is enco ded in t he n1olecular structure of nuclek acids "hich con1e in t\Yo types: d eo.xyribonucle .. ic acid DNA and ribonucleic acid RNA. Nucleic acids are polyn1ers consisting of repeating units called nu cleo .. tides each n ucleotide consists of a sugar a phosphate and a nitrogenous base. The nitrogenous bases in DNA are of four types: adenine A. cytosine C. guanine G and thyn1ine T. The sequ ence of these bases enco des genetk inforn1ation. DNA consists oft\•lo con1plen1entary n ucleo· tide strands . Most organisnls carry their genetic inforn1a .. tion in DNA but a fe. viruses carry it in RNA. The four nitrogenous bases of RNA are adenine Crt:osine g uanine and uracil U. GENES ARE LOCATED ON CHROMOSOMES The vehicles of genetic inforn1ation \\fithin a ceU are chron1oson1es Fig .. ure l .14 \\Thich consist of DNA and associated proteins. The cells of each sped es have a characterlitic nu n1ber of chmn10 .. son1es for exan1 ple. bacterial ceU s norn1 aU y poss.es.s a single chmn1oson1e hun1an celL i possess 46 pigeon cells possess 80. Each chron1 oson1e carries a large nun1ber of genes. CHROMOSOMES SEPARATE THROUGH THE PROCESS· ES OF MITOSIS AND MEIOSIS The processes of mitosl and n1eiosis ensure that a complete set of an organisn1s chron1oson1 es exists in each cell resulting fron1 cell division. .fitosis is the separation of chron1oson1es in the division of Sequence that encodes a trait Chromosome 1.14 Genes are carried on chromosomes. son 1atk. nonsex cells. leiosis is the pairing and separa· tion of chron1oson1es in the division of sex cells to produc. e gametes reproductive cells. GENETIC INFORMATION IS TRANSFERRED FROM DNA TO RNA TO PROTEIN Many genes encod e character· istics by specifying th e structu re of proteins. Genetic in .. forn1ation is first transcribed fron1 DNA into RNA and t hen RNA is translated into th e an1ino acid sequence of a protein. MllTATIONS ARE PERMANENT CHANGES IN GENETIC INFORMATION THAT CAN BE PASSED FROM CELL TO CELL OR FROM PARENT TO OFFSPRING Gene m uta· tions affect the genetic inforn1ation of only a single gene chron1oson 1e n1utations alter the nun1ber or the structure of chron1oson 1es and therefore u su ally affe.:t n1any genes. SOME TRAITS ARE AFFECTED BY MULTIPLE FACTORS Son 1e traits are affected by n1ultiple genes that interact in con1ple.x \Yays \Yith envimnn 1ental factors. Hun1an h eight for exan 1ple is affected b n1any genes as \\leU a.i envimn­ n1ental factors such as n utrition. EVOLllTION IS GENETIC CHANGE Evolution can be vie\\ed as a t\.crstep proces.i: first genetk variation arises and secon dson1 e genetk variants increase in frequency \\lherea.i other variants decrease in frequencr . TRY PROBLEM 24

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lntroduaion to Genetics 13 ••. iiilii"f·•-------------------------- • Genetics is central to the life of every person: it influences a per.ons physkal features personality intelligence and susceptibility to nun1erous diseases. • Genetics plar s inlportant roles in agriculture the pharn1aceutkal industry and n1 edicine. It is central to t he study of biology. • All organisms use sin1ilar genetic systen1s. Genetk variation is the foundation of evolution and is critical to understanding all life. • The study of genetks can be broadly divided into transnlission genetics n1olecular genetks. and population genetics. • lvlod el genetic organisn1s are species about .hich n1uch genetic inforn1ation exists because they h ave characteristics t hat n1ake t hen 1 particularly an1enable to genetic analysis. • The use of genetics by hun1ans began \lith the don1estkation of plants and anin1a.ls. • Ancient Greeks developed t he concepts of pan genesis and t he inheritance of acquired characteristics both of \.hich \/ere later disproven. Ancient Ron1ans developed practical n1easures for th e breeding of plants and anin1als. • Preforn1ationisn1 suggested that a person inherits aU of his or her traits fron1 one parent. Blending inheritance IMPORTANT TERMS genome p. 4 transn1ission genetics p. 5 molecular genetics p. 5 population genetics p. 5 n1odel genetk oani.sn1 p. 5 pangenesis p. S proposed that offspring possess a mtxtu re of the parental traits. These ideas "ere later sho\111 to be incorrect. • By studying t he offspring of crosses beh/een varieties of peas Gregor Mendel d icovered the principles of heredity. Developn1ents in cytology in th e nineteenth century led to t he understanding that t he cell nucleus is the site of heredity. • In 1900 Mendels principles of heredity were redi. scovered. Popu l -ation genetics \\13S established in the early 1930.s followed closely by biocbemical genetks and bacterial and viral genetics. The structure of DNA \/as discovered in 1953 stin1ulating the rise of n1olecular genetks. • Cells are ofn.o basic types: prokaryotk and eukaryotk. • The genes that d etern1ine a trait are tern1ed the genotype the trait that they produce is the phenotype. • Genes are located on c.hron1oson1eSt \Vhich are n1ade up of nucleic acids and proteins and are partitioned into daughter cell s th rough the process of n1itosls or n1eiosls. a Genetic in furn1ation is e:\.-pressed th rough the transfer of inf0rn1ation fmn1 DNA to JUJA to proteins • Evolution requires genetic ch ange in populations. inheritance of acquired characteristics p. S preformationism p. S blending inheritance p. 9 cell theory p. 9 germ-plasm theory p. 9 QLjl.1jfiieliel813§1311iiti-------------------------- I. d 2. No because h orses are expensive to h ouse feed and propagate th e have too fe. progeny and their generation tin1e is too long. 3. Developments in cytology in the 1 800s led to the identification of parts of the cell including the cell nu cleus and ch mn1 oson1es. The ceU theory focused the attention of biologists on the cell eventually leading to the conclusion that the nucleus contains the hereditary inforn1ation. 1+.1•1l§lijli§Lii.11.1114j+t.1p-------------------------- An.s"ers to questions and problen1s preceded by an asterisk can be foun d at the end of the book. Section 1.1 ... 1. Ho. did Hopi culture contribute to t he h igh incidence of albinisn1 an1ong men1bers of th e Hopi tribe 2. Outline son1e of the \.ays in .h k h genetics is in1portant to all of us. 3. Give at least t hree exan1ples of t he role of genetks in society today . 4. Briefly e.xplain .h y genetics is crucial to n1odern biology.

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14 CHAPTER I 5. List the three traditional subdisciplines of genetks and sun1n1ariz.e \/hat each covers. 6. \t\ hat are son1 e characteristics of n1odel genetic organisntot that n1ake then1 us.eful for genetk studies Section 1.2 7. \t\ hen and \\There did agriculture fit arise \r\ hat role did gen et ks play in the development of the first don1estkated plants and aninlals 8. Outline the notion of pangenesis and e.xplain ho\/ it differs from the germ· plasm theory. 9. \r\ hat does the concept of the inheritance of acqu ired characteristks propose and ho\\ is it related to the notion of pan genesis 10. \r\ hat is preforn1ationisn1 \t\ 7 hat did it h ave to say about ho. traits are inherited 11. Define blending lnheritance and contrast it \Tith preforn1ationisn1. 12. Ho. did developn1ents in botany in the seventeenth and eighteenth centuries contribute to the rise of n1odern genetics Section 1.1 17. \r\ hat is the relation bet\.reen genetics and evolution 18. For each of the following genetic topics. indkate \\lhether it focuses on transn1i.s.ston genetics n1olecular genetics or population genetics. a. Analysis of pedigrees to determine the probability of son1eone inheriting a trait b. Study of people on a small island to determine why a genetic forn1 of a.."ithn1a is prevalent on the island c. Eft ect of nonrandon1 n1ating on the distribution o f genotypes among a group of anin1als d. Exan1ination of the nucleotide sequences found at th e ends of ch mn1oson11s e. Mechanisn1s that ensure a high degree of accuracy in DNA replication f. Study of how the inheritance of trails encoded by genes on sex chron1oson1es sex-linked traits differs fron1 the inheritance of traits encoded by genes on nonsex chron1oson1es autoson1al traits 19. Describe son1e of the \\fars in \.rhich your 0\\111 genetic n1akeup affects you a.."i a person. Be as specific as you can. 20. Describe at least one trait that appears to run in your family appears in multiple members of t he family. Does this trait run in your fanllly because it is an inherited trait or because it l caused by environn1ental factors 13. l ist son1e advances in genetics n1ade in th e t\\lentieth century. 14. Briefly explain the contribution that each of the foUO\ V"ing persons n1ade to the study of genetics. a. lvfatthias Schleiden and Theodor Sch\.rann b. August \A/eisnunn c. Gregor Mendel d. Jan1es \"latson and Francis Crkk e. Kary Mullis Section 1.3 15. \A/ hat are the t\iO basic cell types fron1 a structural perspective and ho\i do they differ 16. Outline the relations betwttn genes DNA and chron1os.on1es. For more questions that test your comprehension of the key chapter concepts 90 to LEARNING Curf for th.is ch.apter. that are con1n1on to fan1ily n1en1bers Ho. n1lght rou distinguish beh/een these possibilities Section 1.2 1-21. Genetics is said to be both a very old science and a very young science. E.xplain \\lhat is n1eant by this staten1ent. 22. Match the de.ocription a through d with the correct theory or concept listed belo"· Preforn1ationisn1 Pan genesis Gern1 .. plasn1 theory Inheritance of acquired characteristics a. Each reproductive cell contains a con1plete set of genetic inforrnation. b. All traits are inherited fron1 one parent. c. Genetic inforn1ation n1ay be altered by the use of a characteristic. d. Cells of different tissues contain different genetic inforn1ation. 23. Con1pare and contrast the fullo\ling tdeac about inheritance. a. Pan genesis and germ-plasm theory b. Preforn1ationisn1 and blending inheritance c. The inheritance of acqu ired characteristics and our n1odern theory of heredit

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Introd uction to Genetics 15 Section 1.3 24. Con1pare and contrast the follo.ing tern1s: c. Genotype and phenotype a. Eukaryotk and prokaryotic cells d. DNA and RNA b. Gene and allele e. DNA and c.hron1oson1e iiifJiijICilelllJilt.Jf------------------------ Introduction 25. The type of albinism that ariws with high frequency an1ong Hopi Native An1 ericans discuis.ed in t he introduction to this chapter is n1 ost likely oculocutaneous-albinisn1 type J J due to -a defect in the OCA2 gene on chron1oson1e 1 S. Do son1e research on t he Internet to detern1 ine ho\/ the phenotype of this type of albinism differs from phenotypes of other forms ofalbinisrn in hun1ansand the n1utated genes that result in t hew phenotypes. Hint: Viit the Online Mendelian Inheritance in Man Web site http://www.ncbi.nl m.nih. gov/omim/ and search the database for albinism. Section 1.1 26. \•Ve no\V kno. a great deal about t he genetics of hun1ans and hun1ans are the focus of n1any genetic studies. \\ hat are son-ie of the reasons hun1ans have been the foc us of intensive genetic study Section 1.3 _.. 27. Suppose that life exist..i else\/ here in the universe. All life n1ust contain son1 e type of genetk inforn1ation but alien genon1es n1ight not consist of nuc. lek acids and h ave the san1e features as those found in th e genon1es of life on Earth. What might be the common featu res of aU genon1es no n1atter \/here they exist 28. Ch oose one of the ethk.a1 or social li.sues in parts a t hroug h e and give your opinion on t he is.sue. For backgroun d inforn1ation 1 you n1ight read one of t he articles on ethks n1arked \lith an asterlik in the Suggested Readings section for Chapter I at http:/ /courses.bfwpub.com/ pierce Se. a. Should a persons genetic n1akeup be used in detern1ining h is or her eligibility fur life inst1 ranee b. Should biotechnology companies be able to patent ne\11 sequenced genes c. Should gene t herapy be used on people d. Should genetk testing be made available ror inherited disorders for \lhk h th ere li no treatn1ent or cure 29. A 4S·year old \.ron1an u ndergoes genetic testing and discovers that she li at high risk tOr developing colon cancer and Alzhein1 er disease. Bec.ause her child ren h ave S0of her genes they alio n1 ay be at an increased riik for these diseases. Does she have a moral or legal obligation to tell her children and other close relatives about the results of her genetic testing 30. Suppose that you could undergo genetk testing at age 18 for susceptibility to a genetic disease that \.rould not appear until n1iddle age and h a.i no available treatn1ent. a. \\ hat \VOuld be son1e of the possible reasons IOr having such a genetic test and son1eofthe possible reasons fOr not having the test b. Would you personally want to be tested Explain your reasoning. Go to your 15 to fioo additional learning resources and the Suggested R eadings for this chapter.

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