Ch. 7 Concept Check & Comprehension Questions

Question 1

A form of genetic transfer that involves the uptake of a fragment of DNA from the environment is called ___.

Answer 1

Transformation

Question 2

A bacterial cell with an F factor conjugates with an F- cell. Following conjugation, the two cells would be..

Answer 2

F+

Question 3

Which of the following is a type of plasmid?
A. F factor (fertility factor)
B. R factor (resistance plasmid)
C. Virulence plasmids
D. All of the above

Answer 3

D. All of the above

Question 4

With regard to conjugation, a key difference between F+ and Hfr cells is that an Hfr cell..

Answer 4

Transfers a portion of the bacterial chromosome to the recipient cell

Question 5

In mapping experiments, ___ strains are conjugated to F- strains. The distance between two genes is determined by comparing their ___ during a conjugation experiment.

Answer 5

Hfr, times of entry

Question 6

During transduction via P1,

Answer 6

Any small fragment of the bacterial chromosome may be transferred to another bacterium by a bacteriophage

Question 7

Cotransduction may be used to map bacterial genes that are..

Answer 7

Close together on the bacterial chromosome

Question 8

From the following list, what is the correct order for the steps of transformation?

1. Recombination with the bacterial chromosome
2. Binding of a large DNA fragment to the surface of a bacterial cell
3. Cutting a large DNA fragment into smaller pieces
4. Uptake of DNA into the cytoplasm
5. Degradation of one of the DNA strands

Answer 8

2, 3, 5, 4, 1

Question 9

Some bacterial species preferentially take up DNA fragments from members of their own species. This can occur via..

Answer 9

• competence-stimulating peptide (CSP)

- DNA uptake signal sequences

Question 10

Which is an example of horizontal gene transfer?

Answer 10

All of the above

• the transfer of a gene from one strain of E. coli to a different strain via conjugation
• the transfer of a gene from one strain of E. coli to a different strain via transduction
• the transfer of an antibiotic resistance gene from E. coli to Salmonella typhimurium via transformation

Question 11

A bacterial plague is..

Answer 11

A clear region in a bacterial lawn where the bacteria have been lysed

Question 12

When two different alleles that affect the same trait exhibit complementation, an interpretation is that..

Answer 12

The alleles occur in two different genes

Question 13

The goal of intragenic mapping is to determine the..

Answer 13

Order and distance between mutations in a single gene

Question 14

Describe how gene transfer can explain the growth of colonies on the middle plate.

Answer 14

To grow, the colonies must have functional copies of all five genes. This could occur by the transfer of the met+ and bio+ genes to the met- bio- thr+ leu+ thi+ stain or the transfer of the thr+, leu+, and thi+ genes to the met+ bio+ thr- leu- thi- strain.

Question 15

With regard to studying the mechanism of conjugation, what is the purpose of using a U-tube?

Answer 15

Because bacteria are too small to pass through the filter, the apparatus can determine if direct cell-to-cell contact is necessary for gene transfer to occur.

Question 16

Would his circular DNA molecule be found in an F+ or F- cell?

Answer 16

F+ cell

Question 17

What are the functions of relaxase, coupling factor, and the exporter?

Answer 17

Relaxase is a part of the relaxosome, which is needed for the cutting of the F factor and its transfer to the recipient cell

The coupling factor guides the DNA strand to the exporter

The exporter transports it to the recipient cell

Question 18

How is an F’ factor different from an F factor?

Answer 18

F’ factor carries a portion of the bacterial chromosome, whereas an F factor does not

Question 19

With regard to the timing of conjugation, explain why the recipient cell in the top right is pro- whereas the recipient cell in the bottom right is pro+

Answer 19

Because conjugation occurred for a longer period of time, pro+ was transferred in the conjugation experiment shown in the bottom right

Question 20

Why is the scale of this map in minutes?

Answer 20

The type of map is based on the time of gene transfer in conjugation experiments, which is determined in minutes

Question 21

lacZ started at 16 minutes and galE at 25 minutes

Which of these two genes is closer to the origin of transfer?

Answer 21

The lacZ gene is closer to the origin of transfer

Question 22

Transduction is sometimes described as a mistake in the bacteriophage reproductive cycle. Explain how it is a mistake.

Answer 22

The normal process is for bacteriophage DNA to be incorporated into a phage coat. In transduction, a segment of bacterial chromosomal DNA is incorporated into a phage coat.

Question 23

If these two genes were very far apart on the bacterial chromosome, how would the results have been different?

Answer 23

If the two genes were very far apart, the arg+ gene would never be cotransduced with the met+ gene.

Question 24

If the recipient cell did not already have a lys- gene, could the lys+ DNA become incorporated into the bacterial chromosome? Explain.

Answer 24

Yes by nonhomologous recombination