Lecture_Study_Guide__Microbial_Genetics_II

Microbial Genetics II- Study Guide

What is the definition of a mutation in microbial genetics?

A mutation is a change in the DNA sequence of an organism.

What are mutagens?

Mutagens are agents that cause mutations.

What is the definition of a mutation in microbial genetics?

A mutation is a change in the DNA sequence of an organism.

What are mutagens?

Mutagens are agents that cause mutations.

Define wildtype in the context of microbial genetics.

Wildtype refers to the typical form of a gene or organism as it occurs in nature.

What is meant by reversion in genetics?

Reversion is the process by which a mutated gene returns to its original wildtype sequence.

What is the difference between induced and spontaneous mutation?

Induced mutations are caused by external agents (mutagens), while spontaneous mutations occur naturally without external influence.

Give an example of an induced mutation.

An example of an induced mutation is a change in DNA caused by exposure to radiation.

Give an example of a spontaneous mutation.

An example of a spontaneous mutation is a mistake during DNA replication.

How do mutagens affect mutations?

Mutagens increase the frequency of mutations by altering DNA structure or replication.

What are the three types of point mutations?

The three types of point mutations are missense, nonsense, and silent mutations.

What causes frameshift mutations?

Frameshift mutations are caused by insertions or deletions of nucleotides that disrupt the reading frame.

What are chemical mutagens?

Chemical mutagens are substances that cause mutations through chemical reactions with DNA.

What are nucleoside analogs and what is their effect in cells?

Nucleoside analogs are molecules that resemble nucleotides and can cause base-pairing errors in DNA.

What are intercalating agents and their effects in cells?

Intercalating agents insert themselves between DNA bases, causing insertions or deletions during replication.

How does the nucleotide excision repair pathway work?

The nucleotide excision repair pathway removes damaged DNA segments and replaces them with the correct nucleotides.

How does the photolyase repair pathway function?

The photolyase repair pathway uses light energy to repair UV-induced thymine dimers in DNA.

When would the nucleotide excision repair pathway be used?

It is used when there is bulky DNA damage that cannot be repaired by other mechanisms.

When would the photolyase repair pathway be used?

It is used specifically for repairing UV-induced damage, like thymine dimers.

How does the Ames test determine chemical mutagens?

The Ames test assesses the mutagenicity of a compound by measuring its ability to revert a limited strain of bacteria to a non-lethal phenotype.

Why do we need to start with a strain that has a lethal mutation in the Ames test?

Starting with a lethal mutation allows for the assessment of whether the chemical can reverse the mutation.

How do we know how mutagenic a chemical is from the Ames test results?

The number of colonies that grow on the plate indicates the level of mutagenicity of the tested chemical.

What is the difference between vertical and horizontal gene transfer?

Vertical gene transfer is the transmission of genetic material from parent to offspring, whereas horizontal gene transfer is the transfer of genetic material between organisms of the same generation.

What is recombination in microbial genetics?

Recombination is the process by which genetic material is exchanged between organisms, leading to genetic variation.

What happens during bacterial transformation?

During bacterial transformation, bacteria uptake free DNA from their environment and incorporate it into their genome.

How did Griffith’s Classic experiment support horizontal gene transfer via transformation?

It demonstrated that non-virulent bacteria could become virulent by taking up DNA from heat-killed virulent bacteria.

What happens during bacterial conjugation?

Bacterial conjugation involves the transfer of DNA between two bacteria through direct contact, often via a pilus.

What are the two requirements for bacterial conjugation?

The two requirements are the presence of a donor cell with an F factor and a recipient cell.

What is the F factor in bacterial genetics?

The F factor is a plasmid that contains genes necessary for the formation of a pilus and DNA transfer during conjugation.

Why does the F+ cell not lose its F plasmid after conjugation?

The F+ cell retains its F plasmid during conjugation because it replicates the plasmid and transfers a copy to the recipient cell.

What are Hfr cells and why are they significant?

Hfr cells are high-frequency recombination cells that integrate the F factor into their chromosomal DNA, promoting recombination during conjugation.

What happens during bacterial transduction?

During bacterial transduction, bacteriophages transfer genetic material from one bacterium to another.

What are R plasmids?

R plasmids are plasmids that carry antibiotic resistance genes.

What happens when R plasmids are transferred horizontally?

When R plasmids are transferred horizontally, they can confer antibiotic resistance to recipient bacteria.

Why do we regulate gene expression in bacteria?

Gene expression is regulated to ensure proteins are produced in response to environmental conditions and cellular needs.

What is the Operon model?

The Operon model describes how genes are organized and regulated together in prokaryotic cells.

What is a repressor in genetic regulation?

A repressor is a protein that inhibits gene expression by binding to the operator and blocking transcription.

What is an inducer in the context of operons?

An inducer is a molecule that binds to a repressor and inactivates it, allowing gene expression to occur.

When is the lac operon expressed?

The lac operon is expressed in the presence of lactose and absence of glucose.

What is the location and role of the promoter and regulatory gene in an operon?

The promoter is the region where RNA polymerase binds to initiate transcription; the regulatory gene encodes the repressor protein.

What is the role of CAP and cAMP in gene regulation?

CAP (Catabolite Activator Protein) and cAMP (cyclic AMP) assist in the activation of transcription when glucose is low.

What is the difference between an induced and a repressed lac operon?

An induced lac operon is activated in the presence of lactose, while a repressed lac operon is inactive when glucose is present and lactose is absent.

Define the diphasic growth curve and explain what it signifies.

The diphasic growth curve shows two phases of growth in bacteria, indicating initial lag and subsequent exponential growth; it signifies the adaptation to new growth conditions.