Question 1

Which of the following best describes the role of inverted repeats in a mini-transposon, as shown in the plasmid diagram?

Accepted Answer

They serve as recognition sites for the transposase enzyme, allowing the transposon to be excised and inserted elsewhere in the genome.

Question 2

In a transposon mutagenesis experiment, a pool of bacterial mutants is introduced into a mouse gut. After recovery from fecal pellets, the abundance of certain mutants is greatly reduced. What does this indicate about the disrupted genes in those mutants?

Accepted Answer

The disrupted genes are likely essential for survival or colonization in the mouse gut environment.

Question 3

Which process is most likely to generate paralogous genes within a single species?

Accepted Answer

Gene duplication followed by mutation

Question 4

A mutation changes the codon UAC (tyrosine) to UAA (stop). Which of the following best describes this mutation?

Accepted Answer

Transversion and nonsense mutation

Question 5

Which of the following mechanisms is most likely to protect a bacterial species from novel phage infection upon entering a new environment?

Accepted Answer

Restriction-modification system

Question 6

During methyl mismatch repair, which strand is cleaved and why?

Accepted Answer

The unmethylated strand is cleaved because it is the newly synthesized strand.

Question 7

Which of the following is NOT a type of horizontal gene transfer in bacteria?

Accepted Answer

Gene duplication

Question 8

A bacterial cell acquires a gene for antibiotic resistance from a dead cell in its environment. This process is called:

Accepted Answer

Transformation

Question 9

Which of the following best explains why the human gastrointestinal tract is considered a 'caldron' of horizontal gene transfer?

Accepted Answer

High bacterial density and mixed-species biofilms facilitate frequent genetic exchange.

Question 10

Which of the following is a likely consequence of genome reduction in obligate intracellular pathogens such as Mycobacterium leprae?

Accepted Answer

Accumulation of nonfunctional pseudogenes

Question 11

Which of the following best describes a pathogenicity island?

Accepted Answer

A genomic region acquired by horizontal gene transfer that contains virulence genes

Question 12

Which of the following is the most important mechanism for generating new genes and biochemical processes in microbial genomes?

Accepted Answer

Gene duplication followed by functional divergence through mutation

Question 13

A single mutation due to a tautomeric shift of a thymine occurs prior to DNA replication. Assuming no further mutations, what percentage of progeny will contain the mutant gene after one round of replication?

Accepted Answer

$$50\%$$

Question 14

Gene transfer from one bacterium to another by means of a bacteriophage is called _______, whereas _______ involves the transfer of DNA following cell-to-cell contact.

Accepted Answer

Transduction; conjugation

Question 15

Which of the following is a likely outcome of homologous recombination between direct repeats on a chromosome?

Accepted Answer

Formation of both deletion and duplication mutants

Question 16

Which of the following is true about orthologous genes?

Accepted Answer

They are homologous genes found in different species that evolved from a common ancestral gene.

Question 17

Which of the following best describes the function of the transposase gene in a transposon?

Accepted Answer

It encodes an enzyme that catalyzes the movement of the transposon within the genome.

Question 18

Which of the following is a real-world consequence of horizontal gene transfer in the human gut microbiome?

Accepted Answer

Spread of antibiotic resistance genes among diverse bacterial species

Question 19

Which of the following is a likely result of a frameshift mutation?

Accepted Answer

Alteration of the reading frame, resulting in a completely different amino acid sequence downstream of the mutation

Question 20

Which of the following processes is most likely to result in the formation of a circular DNA molecule that is not replicated and eventually degrades?

Accepted Answer

Homologous recombination between direct repeats leading to deletion

Microbial Genome Evolution, Mutations, and Horizontal Gene Transfer

Study Guide - Practice Questions

Study Guide - Flashcards