Question 1

Which characteristic of bacteria makes them particularly powerful as model organisms for genetic studies?

Accepted Answer

They grow quickly and in large numbers, with a small genome and clear phenotypic markers.

Question 2

What is the primary advantage of selecting for phenotypes (such as antibiotic resistance) rather than screening for them in bacterial genetics experiments?

Accepted Answer

Selection is less labor-intensive and does not require inspection of individual colonies.

Question 3

Which of the following is a possible function of plasmids in bacteria?

Accepted Answer

Plasmids can provide antibiotic resistance or metabolic capabilities.

Question 4

A researcher wants to select for E. coli that can grow using arabinose instead of glucose. Which medium should they use?

Accepted Answer

Minimal medium with arabinose as the sole carbon source.

Question 5

Which mechanism of gene transfer in bacteria requires physical contact between cells?

Accepted Answer

Conjugation

Question 6

In the interrupted mating experiment, what is the purpose of using a blender?

Accepted Answer

To physically separate conjugating bacteria and stop DNA transfer.

Question 7

Which equation best describes the frequency of cotransduction for two genes, given their distance apart on the chromosome?

Accepted Answer

$$f = 1 - \frac{d}{L}$$, where $$d is $$the distance between genes and $$L is $$the length of the phage DNA$

Question 8

Why are recipients generally not converted to F+ or Hfr after conjugation with an Hfr donor?

Accepted Answer

The last part of the F factor is transferred last and is rarely completed.

Question 9

A bacterial strain is auxotrophic for leucine and methionine. Which medium would allow only prototrophic revertants to grow?

Accepted Answer

Minimal medium with no supplements.

Question 10

Which of the following best describes the lytic cycle of a bacteriophage?

Accepted Answer

The phage kills the host cell immediately, producing many new phages.

Question 11

In a conjugation experiment, the order of gene transfer is thr, leu, ton, pro, lac, gal, and azi. Which gene is transferred last?

Accepted Answer

azi

Question 12

Which of the following statements about transformation in bacteria is correct?

Accepted Answer

Transformation involves uptake of free DNA from the environment.

Question 13

A generalized transducing phage sometimes packages bacterial DNA instead of its own. What is the consequence of this event?

Accepted Answer

The packaged bacterial DNA can recombine into the genome of a new host.

Question 14

Which of the following is NOT a reason why E. coli is considered a workhorse of molecular biology?

Accepted Answer

It is diploid, allowing for complex genetic analysis.

Question 15

In mapping the bacterial genome using conjugation, what does the time of entry of a gene indicate?

Accepted Answer

The gene's distance from the origin of transfer.

Question 16

Which equation would you use to calculate the number of generations ($$n) $$given the initial cell number ($$N_0) $$and final cell number ($$N) in a $$bacterial culture?

Accepted Answer

$$n = \log_2$ \left( \frac{N}{N_0$} \right)$$

Question 17

Which of the following is a real-world consequence of gene transfer between bacteria?

Accepted Answer

Spread of antibiotic resistance among pathogenic bacteria.

Question 18

In a U-tube experiment, prototrophic colonies appear only on one side of the filter. What does this indicate about the mechanism of gene transfer?

Accepted Answer

Gene transfer can occur via a small, filterable agent such as a phage.

Question 19

Which of the following best explains why the lysogenic cycle is advantageous for a bacteriophage?

Accepted Answer

It enables the phage to persist in the host genome until conditions are unfavorable.

Genetics of Bacteria: Mechanisms, Mapping, and Model Systems

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