Why are the recombinants produced from an Hfr x F⁻ cross rarely, if ever, F⁺?

Video transcript

Hi everyone. Let's take a look at this practice problem together which of the following best describes the outcome of an F minus cell when HFR binds to an F minus bacteria. So this F it stands for F factor or fertility factor and an F minus cell does not have an F factor. And an HFR cell is a high frequency combination cell and it does contain the F factor, but it's on a chromosome and recall that an F plus cell is a cell that has the F factor on a plasmid. And in order for conjugation to occur, you need to have it occur between a cell without the F factor and a cell with the F factor. And so conjugation can occur in our case. And when we have this occur, we get the following illustration. And so in step one, you'll see you have the HFR cell and it combines with the F minus. The HFR sell it has blue bacterial chromosome with F factor, which is in the bread integrated into it. And then in the F minus sell it has the green plasmid. In step two, you get transfer of some of that chromosome and some of the F factor. And then in step three, recombination is occurring. And lastly instead four, you get the final result with some of the bacterial chromosome integrated into the plasmid. And in our case, none of the F factor was integrated. And so if we take a look at our answers, we can see that to say non recombinant. And we know that recombination does occur as an illustrated in step three. So we can immediately eliminate a, always a non recombinant F plus and C non recombinant. HFR. And so let's go ahead and take a look at B always of recombinant H F R. Well, we do know the combination occurs. So that is true. However, not all of that F factor is usually transferred as illustration step two and sometimes none of it is transferred. And so the F minus cell may or may not receive partial F factor. And so it's not going to become an F H F R cell because it won't get a factor. And so B is incorrect as well. And then if we look at D will remain F minus with recombination, recombination does occur. That's true and it does remain F minus because it does not receive the whole F factor from the H F R and so D is our correct answer. Alright, everyone, I hope you found this helpful and I'll see you for the next practice problem.