Question

. We know that an F+ cell can donate its F plasmid to a recipient cell to create a new F+ cell. But what about an Hfr? Can an Hfr transfer its DNA as well? (yes/no) Please explain your answer. Why did you answer yes or no?

Let’s just assume, for the sake of this exam, that an Hfr cell could transfer DNA. What would the recipient cell look like? What would it be called? F+? F-? Hfr+? Something else altogether? Please explain your answer.

Answer 1

Yes, Hfr can transfer it's DNA as well.

In the cross (conjugation) between Hfr cell and F- cell, frequency of recombination is very high but frequency of transfer of whole F-factor is very low.

Hfr cell acts as donor while F- cell acts as recipient.

To transfer whole chromosomal DNA, it takes 100 minutes in E. coli. In most of the cases, sex pilus (conjugation tube) breaks before transfer of whole chromosomal DNA takes place. So, frequency of transfer of whole F-factor is very low. After the cross between Hfr cell and F- cell, recipient cell remains recipient.

Bacteria in which contains F-factor and a part of chromosomal DNA integrated in it is known as F-prime bacteria. F’ cells are formed from Hfr cell during induction of F- factor from chromosomal DNA in which F-factor carries a portion of chromosomal DNA along with it.

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