Lecture Study Guide_ Microbial Genetics II

Microbial Genetics II - study guide

What is the definition of mutation in microbial genetics?

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

What is a mutagen?

A mutagen is an agent that causes mutations in DNA.

Define wildtype in microbial genetics.

Wildtype refers to the typical form of a species as it occurs in nature, with no mutations.

What is reversion in genetics?

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

What is the difference between induced and spontaneous mutation?

Induced mutations occur due to external factors like chemicals; spontaneous mutations occur naturally without external influence.

Give an example of an induced mutation.

An example of an induced mutation is one caused by exposure to radiation.

Give an example of a spontaneous mutation.

An example of a spontaneous mutation is a natural error during DNA replication.

How do mutagens affect mutations?

Mutagens increase the frequency of mutations by interacting with DNA.

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 in DNA.

What are chemical mutagens?

Chemical mutagens are substances that cause mutations by altering the chemical structure of DNA.

What are nucleoside analogs?

Nucleoside analogs are compounds that mimic nucleotides and can cause errors in DNA replication.

What are intercalating agents?

Intercalating agents are chemicals that insert between DNA bases, causing frameshift mutations.

How does the nucleotide excision repair pathway work?

It removes damaged sections of DNA and replaces them with the correct sequence.

How does the photolyase repair pathway work?

Photolyase detects and repairs UV-induced damage in DNA using light energy.

When is nucleotide excision repair used?

It is used when there is bulky DNA damage, such as thymine dimers.

When is the photolyase repair pathway used?

It is used to directly repair UV-induced DNA damage using light.

What is the Ames test?

The Ames test assesses the mutagenic potential of a chemical by observing its effect on a strain of bacteria.

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

We start with a lethal mutation to identify mutations that reverse the lethal effect.

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

The number of colonies that grow indicates the frequency of mutations caused by the chemical.

What is the difference between vertical and horizontal gene transfer?

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

Define recombination in genetics.

Recombination is the process where genetic material is exchanged between different DNA molecules.

What happens during bacterial transformation?

Bacterial transformation involves the uptake of naked DNA from the environment by a bacterial cell.

How did Griffith’s experiment support horizontal gene transfer?

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

What happens during bacterial conjugation?

Bacterial conjugation is the transfer of genetic material between bacteria through direct contact.

What are the two requirements of bacterial conjugation?

The presence of a donor bacterium with a fertility (F) factor and a recipient bacterium.

What is the F factor?

The F factor is a plasmid that contains genes necessary for bacterial conjugation.

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

Because the F plasmid is replicated and passed on to the recipient cell while remaining in the donor.

What are Hfr cells?

Hfr cells are bacteria with a high frequency of recombination due to the integration of the F factor into their chromosomal DNA.

Why do Hfr cells promote recombination in recipient cells?

Because their chromosomal DNA can be transferred to recipient cells during conjugation.

What happens during bacterial transduction?

Bacterial transduction is the process by which bacteriophages transfer genetic material between bacteria.

What are R plasmids?

R plasmids are plasmids that carry genes for antibiotic resistance.

What happens when R plasmids are transferred horizontally?

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

Why do we regulate gene expression?

We regulate gene expression to ensure that genes are expressed at the right times and in appropriate amounts.

What is the Operon model?

The Operon model explains how genes are regulated together in a functional unit to control expression.

What is a Repressor in the context of gene regulation?

A repressor is a protein that inhibits gene transcription.

What is an Inducer in gene regulation?

An inducer is a molecule that activates gene transcription by inactivating a repressor.

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 in an operon?

The promoter is a sequence where RNA polymerase binds to initiate transcription.

What is the role of the Regulatory gene?

The regulatory gene produces a repressor or activator that controls the operon.

What is the role of CAP and cAMP in the lac operon?

CAP (catabolite activator protein) requires cAMP to bind to the promoter and enhance transcription of the lac operon.

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

An induced lac operon is active and transcribing enzymes for lactose metabolism, while a repressed operon is inactive and not producing these enzymes.

What is a diphasic growth curve?

A diphasic growth curve shows two distinct phases of growth, typically lag and exponential growth, often observed in microbial populations.