Genetics - Introduction - Self-Test

Introduction to Genetics : 

Introduction to Genetics Woodinville Montessori School 9th Grade Biology Alaine Davis

What is Genetics? : 

What is Genetics? For centuries, humans observed _____________ between parents and their children, animals and their offspring, plants and their seedlings It was clear that – somehow – information was being passed along from parents to children, but there was no understanding of the mechanism for this transmittal Genetics is the name we now give to this study of ________ ________. A ________ is a variation of a particular characteristic. For example, if the characteristic is eye color, one person might have blue eyes while another has brown eyes.

What is Genetics? : 

What is Genetics? For centuries, humans observed similarities between parents and their children, animals and their offspring, plants and their seedlings It was clear that – somehow – information was being passed along from parents to children, but there was no understanding of the mechanism for this transmittal Genetics is the name we now give to this study of inherited traits A trait is a variation of a particular characteristic. For example, if the characteristic is eye color, one person might have the trait of blue eyes while another has the trait of brown eyes.

Early Thinking About Genetics : 

Early Thinking About Genetics Biologists first began recording their scientific thinking about genetics in the early ______s. An early theory was the _________ hypothesis, which proposed that the traits of the parents would mix to create offspring with __________ traits Example: white flowers and red flowers would be expected to have offspring with ______ flowers Problem: many observations did not fit this theory. Sometimes red flowers crossed with red flowers resulted in white flowers! The blending hypothesis is __________ accepted

Early Thinking About Genetics : 

Early Thinking About Genetics Biologists first began recording their scientific thinking about genetics in the early 1800s. An early theory was the blending hypothesis, which proposed that the traits of the parents would mix to create offspring with intermediary traits Example: white flowers and red flowers would be expected to have offspring with pink flowers Problem: many observations did not fit this theory. Sometimes red flowers crossed with red flowers resulted in white flowers! The blending hypothesis is no longer accepted

The Father of Genetics : 

The Father of Genetics _______ ________ was an _________ monk with a keen scientific mind In ______ he figured out the idea of genes transmitting information from one generation to the next (although he did not use the word “gene”) Mendel performed experiments on _____ plants, Pisumsativum, in the monastery gardens

The Father of Genetics : 

The Father of Genetics Gregor Mendel was an Austrian monk with a keen scientific mind In 1865 he figured out the idea of genes transmitting information from one generation to the next (although he did not use the word “gene”) Mendel performed experiments on pea plants, Pisumsativum, in the monastery gardens

Gregor Mendel: Unlikely Genius : 

Gregor Mendel: Unlikely Genius He used excellent experimental procedure: Designed his experiments carefully Collected_______ amounts of data Used____________ ________to reach his conclusions The importance of his findings was not appreciated until about______, after his death

Gregor Mendel: Unlikely Genius : 

Gregor Mendel: Unlikely Genius He used excellent experimental procedure: Designed his experiments carefully Collected large amounts of data Used mathematical analysis to reach his conclusions The importance of his findings was not appreciated until about 1900, after his death

Mendel’s Pea Plant Experiments : 

Mendel’s Pea Plant Experiments Left to themselves, pea plants will ____-________(their stamen and carpels are both on the same plant) Mendel cut off the _______ to prevent this. This allowed him to pollinate with what he liked for experimental purposes He pollinated each individual flower by hand

Mendel’s Pea Plant Experiments : 

Mendel’s Pea Plant Experiments Left to themselves, pea plants will self-pollinate (their stamen and carpels are both on the same plant) Mendel cut off the stamen to prevent self-pollination. This allowed him to pollinate with what he liked for experimental purposes He pollinated each individual flower by hand

Experimental Crosses : 

Experimental Crosses If an experimenter crosses the pollen (from stamens) of one flower with the ovary (carpel) of another flower, this is called cross-__________, or “cross.” Example: a purple flower crossed with a white flower is written _____ ___ _____ (“purple crossed with white”)

Experimental Crosses : 

Experimental Crosses If an experimenter crosses the pollen (from stamens) of one flower with the ovary (carpel) of another flower, this is called cross-fertilization, or “cross.” Example: a purple flower crossed with a white flower is written Purple × White (“purple crossed with white”)

Pea Plant Traits : 

Pea Plant Traits Over many years, Mendel studied 7 different pea plant traits. How many can you name?

Pea Plant Traits : 

Pea Plant Traits Over many years, Mendel studied 7 different pea plant traits, shown in the table at right. The first trait listed is dominant.

Genetics Terminology : 

Genetics Terminology Generations Name the three generations most commonly used in genetic studies. (Hint: Begin with the Parental Generation)

Genetics Terminology : 

Genetics Terminology Generations P – parental generation (true-breeding) F1 – filial generation #1 (first generation, offspring of P) F2 – filial generation #2 (second generation, offspring of F1)

Hybrids : 

Hybrids Hybrids are the offspring of two different ____ - __________varieties, e.g. the offspring of a Purple × White cross ___________ differ in only one trait, e.g. everything else is the same except the flower colors are different __________differ in two traits, e.g. different flower colors and different stem lengths Classic _______cross with two heterozygous parents gives phenotypic ratio of 9 : 3 : 3 : 1)

Hybrids : 

Hybrids Hybrids are the offspring of two different true-breeding varieties, e.g. the offspring of a Purple × White cross Monohybrids differ in only one trait, e.g. everything else is the same except the flower colors are different Dihybridsdiffer in two traits, e.g. different flower colors and different stem lengths Classic dihybrid cross with two heterozygous parents gives phenotypic ratio of 9 : 3 : 3 : 1)

Dominant and Recessive : 

Dominant and Recessive ________are alternative forms of genes, like the gene for purple flowers or the gene for white flowers There are ________ alleles and ________ alleles __________ alleles are represented by capital letters __________ alleles are represented by lowercase letters If even one __________ allele is held, it is expressed (shown) __________ allele must have two to be expressed

Dominant and Recessive Alleles : 

Dominant and Recessive Alleles Alleles are alternative forms of genes, like the gene for purple flowers or the gene for white flowers There are dominant alleles and recessive alleles Dominant alleles are represented by capital letters Recessive alleles are represented by lowercase letters If even one dominant allele is held, it is expressed (shown) Recessive allele must have two to be expressed

Slide 22: 

_______________– two alleles the same (either both dominant or both recessive) PP or pp _______________– alleles are different, like Pp Note that the letters are the same for a given characteristic, like flower color, i.e., they are both the letter p

Homozygous & Heterozygous : 

Homozygous & Heterozygous Homozygous – two alleles the same (either both dominant or both recessive) PP or pp Heterozygous – alleles are different, like Pp Note that the letters are the same for a given characteristic, like flower color, i.e., they are both the letter p

Slide 24: 

__________ – the physical manifestation of one’s genes, e.g. blue eyes or brown hair __________ – the genes in your DNA, esp. when represented using letters for the alleles, e.g. BB or bb __________ = brown hair __________ = BB

Phenotype & Genotype : 

Phenotype & Genotype Phenotype – the physical manifestation of one’s genes, e.g. blue eyes or brown hair Genotype – the genes in your DNA, esp. when represented using letters for the alleles, e.g. BB or bb Phenotype = brown hair Genotype = BB

Mendel’s Principle of ___________ : 

Mendel’s Principle of ___________ Principle of __________– the two alleles for a particular trait separate during gamete formation, so only one is passed on to the offspring

Mendel’s Principle of Segregation : 

Mendel’s Principle of Segregation Principle of Segregation– the two alleles for a particular trait separate during gamete formation, so only one is passed on to the offspring

__________ Square : 

__________ Square The _______ Square is a diagram used to determine the __________ of different possible results of a genetic cross It uses the principle of __________. One individual’s genotype consists of two alleles The alleles segregate during formation of ________ (sperm or egg)

Punnett Square : 

Punnett Square The Punnett Square is a diagram used to determine the probability of different possible results of a genetic cross It uses the principle of segregation. One individual’s genotype consists of two alleles The alleles segregate during formation of gametes (sperm or egg)

Punnett Square : 

Punnett Square The Punnett Square only shows __________ and __________, it does not guarantee a particular outcome. What are the possible outcomes and their probabilities if a brown-eyed heterozygous woman and a brown-eyed heterozygous man have a child? If they have four children, will they have one child with each possible genotype? Why or why not?

Punnett Square : 

Punnett Square The Punnett Square only shows possibilities and probabilities, it does not guarantee a particular outcome. What are the possible outcomes and their probabilities if a brown-eyed heterozygous woman and a brown-eyed heterozygous man have a child? Brown eyes (75% chance) or Blue eyes (25% chance) If they have four children, will they have one child with each possible genotype? Why or why not? They might have one child with each genotype, but there is no way of predicting. There is an 0.4% chance ( 1/256) all four children would have blue eyes.

Slide 32: 

How can you tell if an organism with the dominant trait is homozygous or heterozygous? A __________ is performed with a __________ _________ organism. If you have a purple pea plant flower, what is its phenotype? What are its possible genotypes? How can you find out which genotype is true?

Testcross : 

Testcross How can you tell if an organism with the dominant trait is homozygous or heterozygous? A testcross is performed with a homozygous recessive organism. If you have a purple pea plant flower, what is its phenotype? purple What are its possible genotypes? PP or Pp How can you find out which genotype is true? By performing a testcross with a pp (white) flower

Testcross : 

Testcross

Testcross : 

Testcross Are offspring all dominant phenotype? Then P generation was _____________ __________ Do offspring have a 50-50 ratio of dominant to recessive phenotypes? Then P generation was ____________.

Testcross : 

Testcross Are offspring all dominant phenotype? Then P generation was homozygous dominant Do offspring have a 50-50 ratio of dominant to recessive phenotypes? Then P generation was heterozygous.

Slide 37: 

Mendel came up with another important rule about inheritance, called the Principle of ___________ ___________ , which relates to dihybrid (or more complex) crosses. Remember that dihybrid crosses involve crossing organisms that are different in ______ characteristics. An example would be crossing a pea plant with round yellow peas and a pea plant with wrinkled green peas How would we write such a cross? (Hint: round and yellow are the dominant traits for peas)

Principle of Independent Assortment : 

Principle of Independent Assortment Mendel came up with another important rule about inheritance, called the Principle of Independent Assortment, which relates to dihybrid (or more complex) crosses. Remember that dihybrid crosses involve crossing organisms that are different in two characteristics. An example would be crossing a pea plant with round yellow peas and a pea plant with wrinkled green peas How would we write such a cross? RRYY × rryy

Sample Dihybrid Cross : 

Sample Dihybrid Cross Let’s say there is a species of birds, pictured below, that differ in two characteristics—what are those characteristics?

Sample Dihybrid Cross : 

Sample Dihybrid Cross Let’s say there is a species of birds, pictured below, that differ in two characteristics—what are those characteristics? Color and presence/absence of crest. If you took a true-breeding red bird with no crest and a true-breeding blue bird with a crest, as pictured, and all of the offspring were red with a crest, what could you conclude?

Sample Dihybrid Cross : 

Sample Dihybrid Cross If you took a true-breeding red bird with no crest and a true-breeding blue bird with a crest, as pictured, and all of the offspring were red with a crest, what could you conclude? That red is dominant over blue and having a crest is dominant over not having a crest.

Dihybrid Cross : 

Dihybrid Cross What would be the P generation? The F1 generation? (Use A for coloration and C for crest) Write the cross of P × P. Write the cross of F1 ×F1.

Dihybrid Cross : 

Dihybrid Cross What would be the P generation? AAcc (red with no crest) and aaCC (blue with crest) The F1 generation? All AaCc (red with crest) Write the cross of P × P. AAcc × aaCC Write the cross of F1 ×F1. AaCc × AaCc

Dihybrid Cross Punnett Square : 

Dihybrid Cross Punnett Square How does this demonstrate the principle of independent assortment?

Dihybrid Cross Punnett Square : 

Dihybrid Cross Punnett Square How does this demonstrate the principle of independent assortment? Each allele assorts independently of other traits. The genes are randomly inherited with respect to other genes. (Note: we will discuss exceptions)