Question 1

Which of the following best describes the role of the Type VI secretion system (T6SS) in Vibrio cholerae?

Accepted Answer

It facilitates horizontal gene transfer by killing neighboring cells and releasing DNA.

Question 2

A mutation that changes a codon from UAC (tyrosine) to UAA (stop codon) is classified as which type of mutation?

Accepted Answer

Nonsense mutation

Question 3

Which of the following statements about auxotrophs is correct?

Accepted Answer

Auxotrophs have lost the ability to synthesize an essential growth substance due to a mutation.

Question 4

What is the main difference between transitions and transversions in point mutations?

Accepted Answer

Transitions involve purines substituted for other purines, while transversions involve purines substituted for pyrimidines or vice versa.

Question 5

A bacterial strain is designated as hisC2. What does this notation indicate?

Accepted Answer

It is a mutant strain with the second isolated mutation in the hisC gene.

Question 6

Which of the following best explains why single base errors are more likely to result in missense mutations than nonsense mutations?

Accepted Answer

Most single base substitutions encode amino acids rather than stop codons.

Question 7

Which mutagenic agent is most likely to cause frameshift mutations by intercalating between DNA base pairs?

Accepted Answer

Acridine dyes

Question 8

In the context of bacterial conjugation, what is the significance of an Hfr strain?

Accepted Answer

It has an integrated F plasmid and can mobilize chromosomal genes during conjugation.

Question 9

Which of the following is a consequence of a frameshift mutation?

Accepted Answer

Scrambling of the entire polypeptide sequence downstream of the mutation.

Question 10

Which process allows bacteria to acquire DNA from their environment and incorporate it into their genome?

Accepted Answer

Transformation

Question 11

A strain of E. coli is unable to grow at 42°C but grows normally at 30°C. What type of mutation does this strain likely possess?

Accepted Answer

Temperature-sensitive mutation

Question 12

Which of the following best describes the function of the CRISPR system in prokaryotes?

Accepted Answer

It acts as an immune system by targeting and destroying foreign nucleic acids.

Question 13

Which of the following is true regarding the SOS repair system in bacteria?

Accepted Answer

It allows DNA repair to occur without a template, often introducing mutations.

Question 14

A mutation in a gene encoding an enzyme of a metabolic pathway that prevents the use of a specific amino acid as a nitrogen source is best described as:

Accepted Answer

Catabolic mutation

Question 15

Which of the following is a correct statement about transposons?

Accepted Answer

Transposons carry genes for transposase and can move DNA between inverted repeats.

Question 16

Which of the following best explains why RNA viruses have higher mutation rates than DNA viruses?

Accepted Answer

RNA viruses lack proofreading and repair mechanisms.

Question 17

During generalized transduction, which of the following occurs?

Accepted Answer

Any portion of the host genome can be packaged into a phage and transferred.

Question 18

Which of the following is a likely outcome of a second-site reversion?

Accepted Answer

Restoration of wild-type phenotype by a mutation at a different site that compensates for the original defect.

Question 19

Which of the following mutagens acts by resembling normal nucleotide bases but causing faulty base pairing during replication?

Accepted Answer

Base analogs

Question 20

A bacterium is exposed to ultraviolet (UV) radiation. What is the most likely effect on its DNA?

Accepted Answer

Formation of pyrimidine dimers leading to DNA replication errors.

Genetics of Bacteria: Mutation and Gene Transfer

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