Question 1

Which of the following best describes a missense mutation?

Accepted Answer

A mutation that changes one amino acid in the protein sequence to another.

Question 2

A bacterial strain is unable to grow on minimal medium lacking histidine but grows well when histidine is supplied. What is the most likely explanation?

Accepted Answer

The strain is an auxotroph for histidine.

Question 3

Which of the following mechanisms is responsible for the physical exchange of DNA between homologous regions of two DNA molecules in bacteria?

Accepted Answer

Homologous recombination

Question 4

Which protein is essential for homologous recombination in bacteria and is also found in Archaea and most Eukarya?

Accepted Answer

RecA

Question 5

A scientist treats E. coli with ethidium bromide, which intercalates into DNA. What type of mutation is most likely to result?

Accepted Answer

Frameshift mutation

Question 6

Which of the following statements about the SOS response in E. coli is TRUE?

Accepted Answer

The SOS response is regulated by LexA and RecA proteins.

Question 7

Which of the following best explains why frameshift mutations generally have more severe consequences than missense mutations?

Accepted Answer

Frameshift mutations change the reading frame, altering all downstream amino acids.

Question 8

Which process involves the uptake of free DNA from the environment by a bacterial cell?

Accepted Answer

Transformation

Question 9

A bacterium is exposed to UV light, resulting in the formation of pyrimidine dimers. What is the most likely outcome if the damage is not repaired before replication?

Accepted Answer

Cell death or mutations due to errors during DNA replication

Question 10

Which of the following is a key difference between generalized and specialized transduction?

Accepted Answer

Generalized transduction can transfer any gene from the donor, while specialized transduction transfers only specific genes adjacent to the prophage integration site.

Question 11

Which of the following best describes the function of CRISPR-Cas systems in bacteria?

Accepted Answer

They provide adaptive immunity against foreign genetic elements such as viruses.

Question 12

A bacterial cell with an integrated F plasmid is called:

Accepted Answer

Hfr cell

Question 13

Which of the following is TRUE about transposons?

Accepted Answer

They can carry antibiotic resistance genes and move them between DNA molecules.

Question 14

Which of the following is a plausible fate for DNA transferred into a bacterial cell by horizontal gene transfer?

Accepted Answer

It may be degraded, replicate independently, or recombine with the host genome.

Question 15

Which of the following best describes a merodiploid bacterial cell?

Accepted Answer

A cell with two copies of a particular chromosomal segment, usually one on the chromosome and one on a plasmid or phage.

Question 16

Which of the following is a common laboratory use of transposon mutagenesis?

Accepted Answer

To create random mutations for gene function studies.

Question 17

Which of the following is a feature of the F plasmid that allows it to integrate into the E. coli chromosome?

Accepted Answer

It contains insertion sequences (IS elements) homologous to those in the chromosome.

Question 18

Which of the following is a likely outcome if a bacterial cell receives a plasmid carrying a functional wild-type gene that complements a chromosomal mutation?

Accepted Answer

The cell will regain the wild-type phenotype.

Question 19

Which of the following is TRUE regarding horizontal gene transfer in Archaea?

Accepted Answer

It can occur via transformation, conjugation, and virus-like mechanisms, but details often differ from Bacteria.

Question 20

Which of the following best describes the role of restriction endonucleases in bacterial cells?

Accepted Answer

They protect the cell by cutting foreign DNA, such as that from viruses.

Microbial Genetics: Mutations, Gene Transfer, and Genomic Integrity

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