Lecture 16

Question 1

What are the three mechanisms through which bacteria can gain genetic recombination?

Answer 1

Conjugation- transfer of DNA via cell-cell contact
Transformation where there is uptake of naked DNA from the environment
Transduction where there is transfer of genetic material from one cell to another via bacteriophages

Question 2

What is the process of conjugation in bacteria?

Answer 2

An F+ donor cell will produce a pili, this will attach to another F- recipient cell
This attachment allows flow of genetic material through the pili of either just the F gene (if it is a small isolated section of genetic material) or the entire genome of the donor cell (if the F gene has been integrated into the genome as in an Hfr cell)

Question 3

What is an Hfr strain?

Answer 3

A strain which has a high frequency of recombination, and occurs because the F gene has integrated itself into the host genome

Question 4

How can a cell become a partial diploid cell?

Answer 4

F can move out of the host genome in an Hfr back into the cytoplasm and can take some of the bacterial genes with it forming an F’

Question 5

How does the experiment of interrupted mating work and what is its use?

Answer 5

A donor cell is mixed with a population of Hfr cells allowing conjugation to take place
Then at set time intervals remove samples and vortex to break the conjugation bridge
Selective plating can then be used to determine which genes have been transferred to the recipient cell
This process can be used to map the genome of the donor cell