Q: Which equation best describes the rolling circle replication mechanism during conjugation?

$$\text{DNA}_{\text{donor}} \xrightarrow{\text{relaxosome}} \text{ssDNA}_{\text{T strand}} \rightarrow \text{transfer to recipient}$$

Question 1

Which of the following features makes bacteria especially useful for genetic analysis compared to eukaryotes?

Accepted Answer

They have haploid genomes, so mutations are directly observable.

Question 2

A bacterial strain that can grow on minimal medium but not on medium lacking leucine is best described as:

Accepted Answer

An auxotroph for leucine

Question 3

Which process involves the uptake of naked DNA from the environment by a bacterial cell?

Accepted Answer

Transformation

Question 4

In Lederberg and Tatum’s experiment, why did prototrophic colonies appear only when two different auxotrophic strains were mixed and plated on minimal medium?

Accepted Answer

Genetic recombination between the strains restored prototrophy.

Question 5

Which of the following statements about plasmids is FALSE?

Accepted Answer

Plasmids often carry essential genes for bacterial survival.

Question 6

What is the primary function of the F (fertility) plasmid in bacterial conjugation?

Accepted Answer

To promote its own transfer from donor to recipient cells

Question 7

During conjugation between an F+ and an F− cell, what is the outcome for the recipient cell?

Accepted Answer

It becomes F+ and can act as a donor in future conjugations.

Question 8

Which equation best describes the rolling circle replication mechanism during conjugation?

Accepted Answer

$$	ext{DNA}_{	ext{donor}} \xrightarrow{	ext{relaxosome}} 	ext{ssDNA}_{	ext{T strand}} ightarrow 	ext{transfer to recipient}$$

Question 9

In an Hfr × F− mating, why does the recipient cell usually not become a donor?

Accepted Answer

The entire F factor is rarely transferred during conjugation.

Question 10

Which experimental approach is used to determine the order and relative distances of genes on a bacterial chromosome?

Accepted Answer

Interrupted mating (time-of-entry mapping)

Question 11

A bacterium is resistant to streptomycin due to an R plasmid. If this bacterium is used as a recipient in a conjugation experiment, what selective medium would you use to identify exconjugants?

Accepted Answer

Minimal medium with streptomycin

Question 12

Which of the following best describes cotransformation?

Accepted Answer

Simultaneous transformation of two or more genes located close together on a DNA fragment

Question 13

Which step is unique to the lysogenic cycle of a temperate bacteriophage?

Accepted Answer

Integration of phage DNA into the host chromosome

Question 14

In generalized transduction, what determines which bacterial DNA fragment is packaged into a phage head?

Accepted Answer

Random selection based on DNA fragment size

Question 15

A partial diploid (merodiploid) bacterial cell is produced when:

Accepted Answer

An F' plasmid carrying bacterial genes is transferred to a recipient cell

Question 16

Which of the following is a correct equation for the frequency of cotransformation ($$f_{ct}) if $$two genes are transferred together in $$n_{ct}$$ transformants out of $$N$$ total transformants?

Accepted Answer

$$f_{ct} = \frac{n_{ct}}{N}$$

Question 17

Which of the following statements about Hfr strains is TRUE?

Accepted Answer

Hfr strains have the F factor integrated into their chromosome.

Question 18

Which process is responsible for the formation of a heteroduplex during bacterial transformation?

Accepted Answer

Homologous recombination between donor and recipient DNA

Question 19

In a time-of-entry mapping experiment, the gene that appears first in exconjugants is:

Accepted Answer

The gene closest to the origin of transfer (oriT)

Question 20

Which of the following best explains why multiple Hfr strains are needed to construct a complete genetic map of a bacterial chromosome?

Accepted Answer

Each Hfr strain transfers genes in only one direction from its unique integration site.

Genetic Analysis and Mapping in Bacteria and Bacteriophages: Study Notes

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