Question 1

Which of the following is NOT a possible fate for DNA that enters a bacterial cell during horizontal gene transfer?

Accepted Answer

It is immediately transcribed and translated into protein.

Question 2

Homologous recombination in bacteria requires which of the following proteins to facilitate strand invasion?

Accepted Answer

RecA protein

Question 3

In the classic experiment by Fredrick Griffith, which combination of Streptococcus pneumoniae cells led to the transformation of non-virulent cells into virulent ones?

Accepted Answer

Live R cells and heat-killed S cells

Question 4

Which of the following statements about bacterial competence is TRUE?

Accepted Answer

Competence is genetically determined and often involves pili.

Question 5

Natural competence in Bacillus subtilis and Vibrio cholerae is regulated by which process?

Accepted Answer

Quorum sensing

Question 6

During generalized transduction, which portion of the host genome can be packaged into a bacteriophage?

Accepted Answer

Any portion of the host genome

Question 7

Specialized transduction differs from generalized transduction in that:

Accepted Answer

Only specific regions of the host chromosome are transferred.

Question 8

Phage conversion can result in which of the following phenotypic changes in a host cell?

Accepted Answer

Immunity to further infection by the same phage

Question 9

Which of the following best describes bacterial conjugation?

Accepted Answer

Transfer of DNA through direct cell-to-cell contact

Question 10

The F (fertility) plasmid in E. coli contains genes for which of the following functions?

Accepted Answer

Regulation of DNA replication and transfer functions

Question 11

What is the role of insertion sequences in the integration of the F plasmid into the E. coli chromosome?

Accepted Answer

They facilitate homologous recombination between plasmid and chromosome.

Question 12

Why does an Hfr x F- mating not yield two Hfr cells?

Accepted Answer

Only a portion of the integrated F plasmid is transferred.

Question 13

A merodiploid bacterial strain is characterized by:

Accepted Answer

Having two copies of a particular chromosomal segment

Question 14

Which equation best represents the rolling circle replication mechanism used during plasmid transfer in conjugation?

Accepted Answer

$$\mathrm{dsDNA} \rightarrow \mathrm{ssDNA} + \mathrm{ssDNA}$$

Question 15

Which of the following barriers to horizontal gene transfer is mediated by the CRISPR-Cas system?

Accepted Answer

Specific recognition and degradation of foreign DNA

Question 16

Complementation in bacteria occurs when:

Accepted Answer

A functional wild-type gene is supplied on a plasmid or bacteriophage

Question 17

Which of the following best explains why phage conversion is considered beneficial to host cells?

Accepted Answer

It provides immunity to further infection by the same phage.

Question 18

In a laboratory experiment, Trp- cells are mixed with DNA from Trp+ cells and plated on medium lacking tryptophan. What outcome would indicate successful genetic recombination?

Accepted Answer

Growth of colonies on the medium

Question 19

Which of the following is TRUE regarding F' plasmids?

Accepted Answer

They are F plasmids that have excised and captured some chromosomal genes.

Question 20

A researcher wants to induce natural competence in a bacterial culture. Which regulatory mechanism should they consider manipulating?

Accepted Answer

Quorum sensing pathways

9. Mechanisms of Genetic Variation in Prokaryotes: Horizontal Gene Transfer and Recombination

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