QUESTION 1 F+ strain and Hfr strain bacteria are donors and able to transfer genes. True False QUESTION 2 When an F- cell crosses with an F- cell, ___ . F- cell is converted into F+ cell. F- cell is converted into Hfr cell. F- cell is converted into recombinant F- cell. F- cell remains unchanged.
The Correct Answer and Explanation is:
QUESTION 1: F+ strain and Hfr strain bacteria are donors and able to transfer genes.
Answer: True
Explanation:
In bacterial conjugation, an F+ strain is a bacterial cell that contains the F plasmid (fertility plasmid). This plasmid allows the F+ cell to act as a donor, transferring genetic material to another bacterial cell through direct contact. The F+ cell produces a pilus, which facilitates the transfer of the plasmid and sometimes chromosomal DNA to an F- cell, a recipient that lacks the plasmid.
An Hfr strain (High-frequency recombination) is a variant of F+ strain where the F plasmid is integrated into the bacterial chromosome. In Hfr conjugation, the entire bacterial chromosome (or part of it) is transferred along with the F plasmid. This process allows genetic recombination in the recipient F- cell, making Hfr strains powerful tools in mapping bacterial genes.
Both F+ and Hfr strains can transfer genetic material to recipient bacteria, but the type of material transferred differs. F+ cells usually transfer just the F plasmid, while Hfr cells transfer a portion of the chromosome, which can lead to new genetic combinations in the recipient cell.
QUESTION 2: When an F- cell crosses with an F- cell, _______________ .
- Answer: F- cell remains unchanged.
Explanation:
In bacterial conjugation, F- cells are recipients that do not have the fertility (F) plasmid. If two F- cells mate (or come into direct contact), there is no F plasmid in either of the cells to be transferred. Therefore, no gene transfer occurs, and both cells remain F-. This is different from F+ to F- conjugation, where the F+ cell transfers its F plasmid to the F- cell, turning it into an F+ cell. In an F- x F- cross, there is no such transformation, so the F- cells stay as F-.
