Microbial Genetics - DNA Transfer Review of Information Transfer in Cell Recombination Transfer of DNA &Genetic Recombination in Bacteria Conjugation Transformation Transduction

Microbial Genetics - DNA Transfer

Microbial Genetics - DNA Transfer Recombination – process by which DNa is broken and repaired resulting in an exchange of DNA between two DNA molecules to form new combinations of genes Eukaryotic - crossing over during meiosis Prokaryotic - occurs when DNA is transfered from one cell to another (transfer from a doner to a recipient)

Microbial Genetics - DNA Transfer Recombination

Microbial Genetics - DNA Transfer Conjugation

Microbial Genetics - DNA Transfer Normal or Low Frequency Conjugation

Microbial Genetics - DNA Transfer High Frequency Conjugation

Transformation

Transduction

Microbial Genetics - Regulation Three types of regulation Constitutive - gene is always turned on Repression - gene is normally turned on but can be turned off in response to a metabolic signal Induction - gene is normally turned off but can be turned on in response to a metabolic signal

Microbial Genetics - Regulation Regulation of Gene Activity Genes turned on or off as needed - saves energy Enzymes can be regulated by feedback, by control of mRNA sysnthesis or the control of translation

Microbial Genetics - Regulation Three types of regulation Constitutive - gene is always turned on Repression - gene is normally turned on but can be turned off in response to a metabolic signal Induction - gene is normally turned off but can be turned on in response to a metabolic signal

Microbial Genetics - Regulation Types of Regulation of mRNA synthesis Induction - lac operon Repression - trp operon

Microbial Genetics - Regulation

Microbial Genetics - Mutation Mutation - Introduction A mutation is a change in the DNA sequence that results in a change in the product protein Mutations can be neutral, harmful (most) or beneficial Mutation is the basis of variation within a species and thus provides an important mechanism to evolution

Microbial Genetics - Mutation Types of Mutation Base-pair substitution - misssense change in amino acid sequence Base-pair substitution - nonsense change in DNA sequence - premature stop Frameshift Insertion Deletion

Microbial Genetics - Mutation Normal gene DNA transcribed mRNA translated No change in gene product

Microbial Genetics - Mutation Missense mutation Base substitution Changes amino acid sequence by one amino acid May or may not affect activity of protein

Microbial Genetics - Mutation Nonsense mutation Mutation changes codon to stop codon Premature termination of protein Almost always destroys activity of protein

Microbial Genetics - Mutation Frameshift mutation inserts or deletes a base in the DNA Protein may be of correct size (approximately) Protein sequence altered significantly

Microbial Genetics - Mutation Mutatgens Chemicals that modify DNA Deaminating agents Methylating agents Intercalating agents Radiation UV - UV repair system X-Rays

Effect of UV Light Production of Thymine Dimers Repair of Tymine Dimers

Microbial Genetics - Mutation Frequency Rate at which change occurs usually low Mostly random although there are “hot spots” Low rate necessary to provide genetic diversity Rate can change depending upon what population of cells is exposed to