For bacteria that are F⁺, Hfr, F', and F⁻, perform or answer t...

Question

For bacteria that are F⁺, Hfr, F', and F⁻, perform or answer the following.

Which of these donors can transfer a donor gene to exconjugants?

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next problem. It says blank transfers episome consisting of chromosomal genes adjacent to the F factor during conjugation. And our answer choices are a F prime B H F R C F minus and D F plus. So to figure this one out, it's helpful to look at each of these types of cells and remember what makes them distinct to figure out which one transfers chromosomal genes along with the APP factor. So we have an F minus bacterial cell which has no F factor. So that's pretty straightforward since it has no F factor, we actually can eliminate right away as an answer choice because it can't transfer something it doesn't have. So we'll cross out C F minus, then we have an F plus cell which contains the F factor as a separate, we'll say plasmid and that can be transferred to an F minus cell. It can be transferred to a recipient cell, but it just contains the F factor itself does not contain extra chromosomal genes. So that's not what we're looking for either. So we can eliminate choice D F plus if this F factor once transferred into a recipient cell incorporates into the bacterial chromosome, instead of remaining as a separate entity, then you have an H F R cell. So F factor is integrated into the chromosome. And H F R cells can give some of this, some of these genes to a recipient cell during conjugation. However, they're not very efficient at that because they've been integrated, they tend to only transfer a portion before that is interrupted. So let's keep looking because next, we have a case where this H F R cell with the F factor integrated, it is actually excised back out of the chromosome to become a separate plasma again. So F factor excised from the chromosome in an H F R cell taking neighboring chromosomes with it. So we have this F factor that was incorporated into the bacterial chromosome, it's excised back out. But in that process, some of the chromosomes that were on either side of it now become part of this plasma. And in that case, it's now similar to an F plus cell. It's got this separate little plasma that can be donated. But this plasma now has this extra chromosomal material. And that's our F prime cell. And that's what we're looking for because we're looking for the cell that will transfer both the F factor and adjacent genes. So that is the F prime cell that we're looking for, which we find in choice A F prime. And then we'll eliminate the H F R cell, which was to choice B. So again, we have choice A F prime transfers episome consisting of chromosomal genes adjacent to the F factor during conjugation. See you in the next video.

For bacteria that are F⁺, Hfr, F', and F⁻, perform or answer the following.
Which of these donors can transfer a donor gene to exconjugants?

Key Concepts

Conjugation in Bacteria

F⁺ and Hfr Strains

F' Strains

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