Conjugation between an Hfr cell and an F⁻ cell does not usually r...

Question

Conjugation between an Hfr cell and an F⁻ cell does not usually result in conversion of exconjugants to the donor state. Occasionally, however, the result of this conjugation is two Hfr cells. Explain how this occurs.

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next problem. It says the outcome of conjugation between an H F R cell and an F minus cell can result in two H F R cells because of all of the following reasons except choice. A, an error in the homologous recombination process. B the conjugation junction is disrupted at the location where the F factor is integrated. C the F factor carries a part of the bacterial chromosome which is integrated into the recipient cell and D transfer genetic material remains in the recipient cell allowing it to recombine with its chromosome. Well, we can recall that in general, unlike when you have an F plus cell crossed with an F minus cell, which results in the transfer of the F factor, meaning that the F minus cell becomes an F plus cell. When you have an H F R cell crossed with an F minus cell, the F minus cell remains F minus as a rule. Or in general, as we recall, what makes an H F R cell is that the um F factor that was originally on a separate plasmin has become incorporated into the bacterial chromosome. And as part of that conjugation process, the chromosome gets nicked at the F factor and begins to transfer a single strand into the F minus cell. So as we think about that process, we're supposed to look at a reas reasons why you would actually end up with 2 HFR cells. So why wood and F minus cell end up as in H F R? So even though that's not usually what happens, and the answer that the one last trick is that the answer we're looking for is something that is not a reason. So three of these answer choices are reasons why that might happen. And one is an exception for what is not a reasonable. So choice A says an error in the homologous recombination process. Well, we've kind of hit upon our choice right away. This would not be a reason why your F minus cell would be converted to an H F R cell because homologous recombination is how it gets converted into an H F R cell in the first place. So that would not be a reason why it would be. Choice. B says a conjugation junction is disrupted at the location where the F factor is integrated. Well, this could cause the cell to be converted to an H F R cell. Uh if there's a disruption um where the F factor is integrated, that could prevent that chromosome from being nicked open at that point and result in the transfer of the entire chromosome rather than just a little bit of it and end up converting that F minus cell into an H F R cell. So that's why choice B is not our answer. Choi says the F factor carries part of the bacterial chromosome which is integrated into the recipient cell. Well, this is also not correct. Um if that F factor and bacterial chromosome are integrated into the recipient cell, that is what converts a cell into an H F R cell. So that would be a reason why you might end up with two H F R cells at the end. And finally, transfer genetic material remains in the recipient cell allowing it to recombine with its chromosome. Again, the key here is that recombination is what transforms an F minus cell into an H F R cell. So that could also be a reason uh why you would end up with that transformation. So choice D is not correct. So again, the outcome of conjugation between an H F R cell and an F minus cell can result in two H F R cells because of all the following reasons except choice a, an error in the homologous recombination process. See you in the next video.

Conjugation between an Hfr cell and an F⁻ cell does not usually result in conversion of exconjugants to the donor state. Occasionally, however, the result of this conjugation is two Hfr cells. Explain how this occurs.

Key Concepts

Hfr and F⁻ Cells

Conjugation Process

Recombination and Gene Transfer

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