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Premium member Presentation Transcript Microbial Genetics: Microbial Genetics Chapter 8Structure and Function of Genetic Material: Structure and Function of Genetic Material DNA & RNA DNA deoxyribonucleic acid RNA ribonucleic acid Nucleotides Phosphate group Pentose sugar Nitrogenous baseStructure of DNA: Structure of DNA Double stranded (double helix) polymers of nucleotides 5’ to 3’ (strands are anti-parallel) Complimentary Base Pairing A - T G - CDNA Replication: DNA Replication Bacteria have only 1 chromosome (ccDNA) E. coli about 4 million base pairs 1 mm long (1000 times longer than the cell) DNA takes up only about 10 % of cells volumeSlide 7: E. coli DNA 1u 1,360u 1ft. 1,360 ft.DNA Replication occurs at the Replication Fork (5’ to 3’): DNA Replication occurs at the Replication Fork (5’ to 3’) DNA Helicase 1. Leading Strand ( 5’ to 3’ ) DNA Polymerase 2. Lagging Strand ( 5’ to 3’) RNA Polymerase (RNA Primer) DNA Polymerase (extends primer and digests RNA) DNA Ligase Okazaki FragmentsBidirectional replication: Bidirectional replication Origin of replication Termination siteProtein Synthesis: Protein Synthesis DNA mRNA Protein Transcription Translation Central Dogma of Molecular GeneticsTranscription: Transcription One strand of DNA is used as a template to form a complimentary strand of mRNA mRNA ----> messenger RNATranscription: Transcription 3 ways RNA differs from DNA Promoter RNA Polymerase Termination Site 5’ to 3’3 Types of RNA: 3 Types of RNA 1. mRNA Contains the codons 2. rRNA Ribosomes (70S) 3. tRNA Transfer amino acids to the ribosomes for protein synthesis Anti-codonGenetic Code: Genetic Code DNA mRNA tRNA Triplet code codons anticodonsGenetic Code: Genetic Code Codons code for a specific amino acid 20 amino acids 3 base code - 4 bases ( A,U,G,C ) 64 possible combinations ( 4 3 ) Amino acids are coded for by more than one codon Genetic Code is Degenerative Genetic Code is UniversalTranslation: Translation rRNA ribosomal RNA (forms the ribosomes) (70S) tRNA transfer RNA (transfers amino acids to the ribosomes for protein synthesis) anticodon 3 base sequence that is complimentary to the codon on mRNARegulation of Gene Expression: Regulation of Gene Expression All Genes are not always being expressed Genes turned on all the time - Constitutive Other genes can be regulated: Turned On Turned Offlac operon: lac operon Lac - Lactose (dissacharide) Glucose and Galactose operon - series of structural genes all under the control of a Regulatory Gene lac operon is normally turned off lac operon is an Inducible operonTryptophan operon: Tryptophan operon Tryptophan - amino acid operon - series of structural genes all under the control of a Regulatory Gene Tryptophan operon is normally turned on Tryptophan operon is a repressible operonMutations - a change in the base sequence of DNA: Mutations - a change in the base sequence of DNA Mutations can be: 1. Harmful 2. Lethal 3. Beneficial 4. Silent (neutral) UUU - Phe UUC - PheSlide 28: Types of Mutations Normal DNASlide 29: Base Substitution Mutation C Missense MutationSlide 30: T Nonsense Mutation Base Substitution MutationFrame Shift Mutation: Frame Shift Mutation ATG CAT GCA TGC ATT TCC TGC TTA AAA 1. Addition Mutation A AT GCA TGC ATG CAT TTT CCT GCT TAA Reading Frame is Shifted 2. Deletion Mutation TGC ATG CAT GCA TTT CCT GCT TAA Reading Frame is ShiftedGenetic Transfer in Bacteria: Genetic Transfer in Bacteria Genetic Transfer - results in Genetic Variation Genetic Variation - is needed for Evolution 3 Ways Genetic Transfer can occur in Bacteria 1. Transformation 2. Cunjugation 3. TransductionTransformation: Transformation Genes are transferred from one bacterium to another as “naked” DNA Frederick Griffith (1928)Griffith’s Experiment: Griffith’s Experiment 2 Strains of Streptococcus pneumoniae 1. Virulent strain with a capsule - Pneumonia 2. Avirulent strain without a capsule - no diseaseSlide 35: Griffith’s ExperimentSlide 36: Griffith’s ExperimentSlide 37: Griffith’s ExperimentSlide 38: Griffith’s ExperimentSlide 40: Conjugation One bacterium passes some DNA (in a plasmid) to another bacteriumTransduction: Transduction DNA is transferred from one bacterium to another by a virus Bacteriophage virus that only infects bacteria You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.