Flashcards in Chapter 7 Questions Deck (15)
What is the role of plasmids?
They carry genes that are not essential to bacterial function but may play an important role in the growth and lifecycle of the bacterial host. Some promote mating and other encode compounds that kill bacteria. They contain an origin of replication.
Which process of DNA transfer in bacteria requires a virus?
What does conjugation depend on?
A fertility factor present in the donor cell and absent in the recipient cell. The F+ cell creates sex pili that make contact with the F- cell. Most genes transferred conguation between the 2 cells are on the F factor.
What site on the F factor enters the recipient cell first?
oriT site. It is always nicked at this site.
What happens in Hfr cells? (High frequency recombination)
The F factor is integrated into the bacterial plasmid. The chromosome follows the F factor into the recipient cell.
What are F' cells?
Cells containing an F plasmid with some bacterial genes. When an F factor is removed from the bacterial chromosome, a small amount of bacterial chromosome may be removed with it.
Present as a separate circular plasmid, donor.
No F factor, recipient.
F factor integrated into bacterial chromosome, high frequency donor.
Present as a separate circular plasmid carrying some bacterial genes, donor.
F+ x F-
Two F+ cells
Hfr x F-
One Hfr cell and one F- cell
F' x F-
Two F' cells
What does antibiotic resistance in bacteria result from?
The action of genes located on R plasmids, small circular plasmids that can be transferred by conjugation.