Q: Which of the following equations best represents rolling circle replication of a plasmid during conjugation?

$$\text{dsDNA} \rightarrow \text{ssDNA} \rightarrow \text{dsDNA}$$

Question 1

Which of the following best describes the difference between generalized and specialized transduction in bacteria?

Accepted Answer

Generalized transduction involves the transfer of any part of the bacterial genome by a bacteriophage, while specialized transduction transfers only specific genes near the phage integration site.

Question 2

A bacterial strain is unable to grow on minimal medium but grows when the medium is supplemented with the amino acid tryptophan. What is the most likely explanation for this phenotype?

Accepted Answer

The strain is an auxotroph for tryptophan.

Question 3

Which of the following mutations is most likely to result in a truncated, nonfunctional protein?

Accepted Answer

Nonsense mutation

Question 4

A frameshift mutation occurs when:

Accepted Answer

A nucleotide is inserted or deleted, changing the reading frame of the genetic code.

Question 5

Which of the following statements about the SOS repair system in bacteria is TRUE?

Accepted Answer

It is activated by extensive DNA damage and allows replication to continue, often introducing mutations.

Question 6

In bacterial conjugation, what structure is responsible for bringing donor and recipient cells into contact?

Accepted Answer

Sex pilus

Question 7

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

Accepted Answer

Frameshift mutations alter the reading frame, affecting all downstream codons and often resulting in a nonfunctional protein.

Question 8

A bacterial cell is exposed to UV light, resulting in the formation of thymine dimers. Which type of mutation is most likely to occur?

Accepted Answer

Mutation caused by non-ionizing radiation

Question 9

Which of the following is a key feature shared by both insertion sequences (IS) and transposons?

Accepted Answer

Both contain genes encoding transposase and have inverted repeat sequences at their ends.

Question 10

A bacterium undergoes transformation. Which of the following must be TRUE for the process to occur successfully?

Accepted Answer

The bacterium must be competent to take up free DNA from the environment.

Question 11

Which of the following equations best represents rolling circle replication of a plasmid during conjugation?

Accepted Answer

$$	ext{dsDNA} ightarrow 	ext{ssDNA} ightarrow 	ext{dsDNA}$$

Question 12

Which of the following best describes the CRISPR system in bacteria?

Accepted Answer

It is an adaptive immune system that stores viral DNA sequences and uses them to target and destroy invaders.

Question 13

A bacterial cell with the F plasmid integrated into its chromosome is called:

Accepted Answer

Hfr cell

Question 14

Which of the following is an example of a selectable mutation?

Accepted Answer

A mutation that confers antibiotic resistance.

Question 15

Which of the following statements about reversion is correct?

Accepted Answer

Same site reversion restores the original DNA sequence at the site of mutation.

Question 16

Which of the following best describes the difference between screening and selection in identifying bacterial mutants?

Accepted Answer

Selection allows only mutants with a specific trait to survive, while screening involves examining many organisms for visible differences.

Question 17

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

Accepted Answer

Transition

Question 18

A point mutation is defined as:

Accepted Answer

A mutation that involves a single base pair.

Question 19

Which of the following best explains why the phenotype of an organism does not always change when its genotype changes?

Accepted Answer

Some mutations, such as silent mutations, do not alter the protein or trait expressed.

Question 20

Which of the following is TRUE regarding Hfr conjugation?

Accepted Answer

Chromosomal genes are commonly transferred, but the entire F plasmid is rarely transferred.

ch 9

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