Question 1

Which of the following best describes a missense mutation?

Accepted Answer

A mutation that changes a codon for one amino acid into a codon for a different amino acid.

Question 2

A researcher exposes bacteria to a chemical that distorts the DNA helix, leading to single nucleotide pair insertions and deletions. Which type of mutagen is most likely responsible?

Accepted Answer

Intercalating agent

Question 3

Which repair mechanism is responsible for correcting damage that causes distortions in the DNA double helix by removing the damaged portion and synthesizing new DNA using the intact strand as a template?

Accepted Answer

Excision repair

Question 4

During homologous recombination in bacteria, which protein is essential for catalyzing the strand invasion and exchange process?

Accepted Answer

RecA

Question 5

A bacterial cell acquires a new gene from a virus that accidentally packaged host DNA during the lytic cycle. What is this process called?

Accepted Answer

Generalized transduction

Question 6

Which of the following statements about frameshift mutations is correct?

Accepted Answer

They result from the insertion or deletion of base pairs in the coding region of a gene.

Question 7

In the context of bacterial conjugation, what is the role of the F factor?

Accepted Answer

It contains the information for formation of the sex pilus and assists in plasmid integration.

Question 8

A mutation that restores the wild-type phenotype by a second mutation at a different site than the original mutation is called:

Accepted Answer

Suppressor mutation

Question 9

Which of the following best describes the process of bacterial transformation?

Accepted Answer

Uptake of naked DNA by a competent cell followed by incorporation into the genome.

Question 10

Which of the following is a characteristic of specialized transduction?

Accepted Answer

Only specific portions of the bacterial genome are transferred by temperate phages.

Question 11

A scientist observes that a bacterial strain can grow on minimal media after a second mutation, even though the original mutation made it auxotrophic. What is the most likely explanation?

Accepted Answer

A suppressor mutation has occurred.

Question 12

Which of the following is true regarding transposable elements?

Accepted Answer

They are segments of DNA that can move about the genome.

Question 13

Which of the following best describes the process shown in the first image (homologous recombination)?

Accepted Answer

A single-stranded segment from donor DNA invades recipient DNA, facilitated by RecA, leading to crossover and exchange of genetic material.

Question 14

In the context of the second image (Hfr conjugation), what is the outcome if the entire F factor is not transferred to the recipient cell?

Accepted Answer

The recipient cell remains F− but may acquire new chromosomal genes.

Question 15

Which of the following equations best represents the mutation rate per cell division if $$N is $$the number of mutants and $$T is $$the total number of cells?

Accepted Answer

$$\mu = \frac{N}{T}$$

Question 16

Which of the following is NOT a possible effect of a point mutation in a protein-coding gene?

Accepted Answer

Conversion of a codon to a transposon.

Question 17

Which of the following statements about horizontal gene transfer (HGT) is correct?

Accepted Answer

HGT allows genes to be transferred between different species, contributing to evolution and increased virulence.

Question 18

Which of the following best describes the function of transposase in simple transposition?

Accepted Answer

It catalyzes the excision and integration of the transposable element.

Question 19

A scientist uses replica plating to identify bacterial colonies that cannot grow on minimal media but can grow on complete media. What type of mutant is being detected?

Accepted Answer

Auxotrophic mutant

Question 20

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

Accepted Answer

Generalized transduction can transfer any part of the bacterial genome, while specialized transduction transfers only specific portions.

Mechanisms of Genetic Variation in Microorganisms

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