Question 1

Which feature of bacterial genomes makes them particularly useful for genetic analysis and the direct observation of mutations?

Accepted Answer

Haploid genomes, so mutations are immediately observable

Question 2

A researcher wants to identify auxotrophic mutants in a bacterial population. Which experimental approach would best allow her to distinguish auxotrophs from prototrophs?

Accepted Answer

Use replica plating to transfer colonies from complete medium to minimal medium and identify those that fail to grow

Question 3

Which type of plasmid is responsible for the transfer of antibiotic resistance genes between bacterial cells?

Accepted Answer

R (resistance) plasmid

Question 4

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

Accepted Answer

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

Question 5

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

Accepted Answer

Transformation

Question 6

In the classic Lederberg and Tatum experiment, why did prototrophic colonies appear when two auxotrophic strains were mixed and plated on minimal medium?

Accepted Answer

Genetic recombination between the two strains via conjugation

Question 7

What did Bernard Davis' U-tube experiment demonstrate about bacterial conjugation?

Accepted Answer

Physical contact between cells is required for genetic recombination

Question 8

Which structure is responsible for the physical connection between donor and recipient cells during bacterial conjugation?

Accepted Answer

Conjugation pilus

Question 9

What is the role of the relaxosome during F factor conjugation?

Accepted Answer

It binds the origin of transfer (oriT) and cleaves one strand of the F factor DNA

Question 10

Which process is used to map the relative positions of genes on a bacterial chromosome using Hfr strains?

Accepted Answer

Interrupted mating and time-of-entry mapping

Question 11

If an Hfr strain transfers genes to an F- recipient, what is the most likely outcome for the recipient cell?

Accepted Answer

It remains F- but may acquire donor alleles via homologous recombination

Question 12

A student performs an interrupted mating experiment with an Hfr strain and observes that the thr gene appears in exconjugants at 5 minutes, leu at 8 minutes, and gal at 25 minutes. What does this suggest about the relative positions of these genes?

Accepted Answer

thr is closest to oriT, followed by leu, with gal farthest away

Question 13

Which equation best describes the relationship between gene transfer time and distance from the origin of transfer in Hfr mapping?

Accepted Answer

$$d = v 	imes t$$

Question 14

What is the main difference between generalized and specialized transduction?

Accepted Answer

Generalized transduction transfers random bacterial DNA; specialized transduction transfers specific genes near the prophage integration site

Question 15

A bacteriophage infects a donor cell and accidentally packages a fragment of host DNA instead of its own genome. This phage then infects a recipient cell, and homologous recombination occurs. What is this process called?

Accepted Answer

Generalized transduction

Question 16

Which of the following best describes rolling circle replication during bacterial conjugation?

Accepted Answer

Replication starts at oriT and displaces the 5' end of the T strand, allowing transfer to the recipient

Question 17

In a real-world scenario, why is the transfer of R plasmids among bacterial populations a major concern in hospitals?

Accepted Answer

It can result in the rapid spread of antibiotic resistance among pathogenic bacteria

Question 18

Which of the following statements about partial diploids (merodiploids) in bacteria is correct?

Accepted Answer

They contain two copies of specific genes present on both the chromosome and an F' plasmid

Question 19

A scientist wants to select for exconjugant cells that have received a donor allele conferring streptomycin resistance. Which medium should she use?

Accepted Answer

Medium containing streptomycin

6. Genetic Analysis and Mapping in Bacteria and Bacteriophages

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