Conjugation: Hfr & F' Cells - Video Tutorials & Practice Problems
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1
concept
Hfr Cell Conjugation
Video duration:
9m
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in this video, we're going to begin our lesson on the conjugation of HFR cells as well as the conjugation of F. Prime cells. However, in this video we're only going to focus on the congregation of HFR cells and then later in a different video will focus on the conjugation of F. Prime cells. And so in order to understand HFR sell conjugation. It's first important to highlight an important fact and that is that F plasmas have the reversible ability to integrate itself into the host chromosome and it can also X. Ice or remove itself from the host chromosome. And so an HFR cell where the HFR really stands for high frequency of recombination. These HFR or high frequency of recombination cells are simply cells that have an F. Plasmid integrated into the host chromosome. And so if we take a look at our image down below, specifically on the left hand side over here, notice that this box is focused on the reversible HFR cell formation and so notice that the top cell that you see here is actually the same F. Plus cell that we talked about in our previous lesson videos because it's a cell that contains the entire F. Plasma and therefore it forms this Pelous that you see over here. Now again, this F plasmid has the ability reversible ability to integrate itself into the chromosome. And so that means that this plasma has the ability to integrate here into the DNA of the host. And so when it does integrate represented by this blue arrow down below, that is what forms the HFR cell. And so the HFR cell is a cell that has an integrated F. Plasmid into the chromosome. As you see here in this image. Now again, the integration of this F plasma is reversible. Which means that the F plasmid can excites itself or remove itself to become the F. Plasmid again. And so that's what we see here with the X. Ices arrow pointing back upwards, shows you that the F. Plasmid once again can come back out uh and become an F. Plus cell. And so what we can see here is that F. Plus cells and HFR cells can be converted into each other depending on the integration status of the F plasma, if the F plasmid is integrated, it's an HFR cell. Whereas if the F plasma is not integrated it's an F. Plus cell. Now. In our last lesson video we were able to talk about the congregation of these F. Plus cells. And so in this video we're gonna be focusing on the congregation of these HF ourselves. And so during the conjugation of the HF ourselves, these HF ourselves are going to serve as the donor cells and the transfer of chromosome away DNA to uh the recipient salvia conjugation. And so instead of only transferring the F. Plasmid and HFR sell conjugation part of the donor cells chromosome all D. N. A. Is going to be transferred. And that is a big difference from what we saw in our previous videos. Now, what we'll see is that there are also some similarities between the conjugation of HF ourselves chromosomal DNA uh and the conjugation of the F. Plasma and e coli uh there are some similarities between the two. However there are also some key differences. And so um some of those key differences include the fact that HFR cells they are going to be making the F pillows to congregate with the f minus L. However the entire integrated F. Plasmid is not going to be transferred to the recipient. Which means that at the end of conjugation the recipient is still going to remain f minus. And so the recipient stays f minus um from the beginning to the end of the congregation process. And so this is very different than what we've seen in our previous videos where both cells were F. Plus at the end of congregation. However, here with HFR sell congregation, the recipient stays F minus. And this is again because the recipient does not receive the entire F plasma. Now again we can emphasize that only a really really small portion only small portions of the donor cells uh chromosomal DNA as well as small portions of the f plasma are going to be transferred to the recipient. And so um that transfer D. N. A. That the f minus recipient cell receives is either going to integrate into the recipient cells, host chromosome or it will be degraded and have no effect. And so if we take a look at our image down below, we can get a better understanding of HFR sell conjugation. Now, over here on the left we're showing you an HF our cell which once again is a cell who has the F. Plasmid integrated into the chromosome. And so here you can see the F plasma is integrated into the chromosome and notice that in this chromosome, just for the sake of an example, we've included three genes, gene A gene B and jean C. And so this HFR sell because it has an integrated F plasma, it's capable of forming the F pellets and it's going to be the donor cell in this uh conjugation process and the other cell that's over here, this is going to be an f minus sell the recipient that does not have the F plasma at all. And so notice that over here we've also added uh in the recipient cells chromosome, these specific genes lower case a prime, lower case B. Prime and lower case C. Prime. So that you can distinguish the f minus cells recipient chromosomal genes uh from the HFR cells, chromosomal genes. And so first what we're going to see is that the HFR cell is going to initiate congregation. And so the HFR cell forms and F pillows which combined to the f minus sell as we see right here and then what we're going to see is that um part of the only part of the integrated F. Plasmid is going to be transferred and only part of the host chromosomes genes is going to be transferred. So in this image only genes A. And B. Are being transferred to the recipient. But jean C. Is not being transferred to the recipient. And so because the recipient only receives portions small portions of the integrated F. Plasma and small portions of the host chromosomally D. N. A. Uh it is going to remain f minus. And so what you can see here is that in this next image that we have down here, the transfer D. N. A. In the f minus cell is going to have the ability to integrate into the chromosome. And so you can see that the transfer D. N. A. Is actually right here. And you can see that there's a small portion of the F. Plasma and there's only portions of the chromosomal genes being transferred. Only genes A. And B. But not gene C. And so what you can see is that at the very end of this process after this portion integrates via homologous recombination. After integration of genes A. And B. It replaces the D. N. A. And that DNA that replace is going to be degraded. So you can see that the degraded D. N. A. Of the host chromosome is here and uh the these jeans here have integrated in and the cell at the end is going to remain once again f minus and it remains f minus because it does not have the entire F plasma. And so it only receives a small portion of the f plasma. Uh And so because it only contains part of the F plasma, it remains f minus and the initial donor cell is still going to remain HFR. And so what has happened in this process is that the HFR cell has transferred over some of its genes, in this case gina and jean B over to the recipient. And it is also transferred over only a portion small portion of the F plasma. And so the recipient remains F minus, which means it's not capable of initiating conjugation, but it has received genes from its neighbor through horizontal gene transfer. And so this year concludes our brief introduction to HFR sell conjugation and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video
2
Problem
Problem
Hfr strains of bacteria:
A
Do not have an F plasmid.
B
Have an F plasmid.
C
Have an F factor integrated in the bacterial chromosome.
D
Have a partial F plasmid as a linear fragment in the cytoplasm.
3
Problem
Problem
What is transferred between two bacterial cells in Hfr conjugation?
A
A small portion of the integrated F plasmid from the Hfr donor cell.
B
A small, random portion of the Hfr donor's cells chromosome.
C
A small portion of the Hfr donor cell's chromosome and integrated F plasmid.
4
concept
F’ Cell Conjugation
Video duration:
4m
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in this video, we're going to begin our lesson on F. Prime cell conjugation where the little apostrophe here is the prime and so first we need to recall from our previous lesson videos that F plasma integration into the host chromosome is a reversible process that can regenerate F plus cells when the entire F plasmid is X. Iced. However, the excision process of this integrated F plasma is air prone and so on some occasions, donor DNA can actually be X. Iced with the F plasma creating what we call F prime cells. And so F prime cells are really just cells that have an ex iced F plasma that contains a small fragment of the cells chromosome, all DNA. And so if we take a look at our image down below, we can get a better understanding of these F prime cells and we're going to focus specifically on the top half of this image which is showing you F. Prime cell formation. And so in this uh image which will notices on the far left, we're showing you the original F plus cell that we talked about in our previous lesson videos which again is going to be a cell that contains the entire F. Plasmid, allowing it to form a pitiless as you see here now recall that the F plasmid has the reversible ability to integrate itself into the host chromosome. And so when it does integrate it forms the HFR cell. So the HFR cell contains the integrated F plasma. And recall that this is a reversible process. So the integrated F plasma can also excites itself back out to form the F plus cell again, so notice we have the arrow going forward and backward to represent this is a reversible process. However, on occasion when the integrated F plasma X ice is itself or removes itself, it is an error prone process. And so occasionally some donor DNA will be excited with the F plasma to create the F. Prime self. And that's what we're showing you over here on this part of the image where the integrated F. Plasmid over here in the HFR self can excites itself and remove part of the chromosomal DNA along with it and that generates over here the F crime cell. And what you'll notice about the F. Prime cell is that the F plasma, the entire F plasma is X. Iced. But so is a small fragment of the chromosomal DNA. And so this here we call this an F. Prime cell. Now in regards to the conjugation of an F. Prime cell. It's important to note that the F prime cells serve as the donor cells and congregations. And so they're able to congregate with f minus recipient cells. And so when they congregate with F minus recipient cells, the F prime cells transfer the chromosomal DNA. That was ex iced as well as the entire f plasma. And so this means that the recipient cell, the F minus recipient cell is going to end up becoming an F. Prime cell as well. And so if we take a look at our image down below, we can get a better understanding of F prime cell conjugation. And so notice on the far left over here we're showing you the F. Prime cell which again is going to serve as the donor cell in congregation. And so notice that the F. Prime cell once again contains the excites plasma that has some chromosomal D. N. A. And the entire F plasma here. And so the donor F. Prime cell is able to congregate with the recipient F minus sell and transfer this entire F. Prime plasma. And when it does so, both cells are going to end up being F crime. The donor cell is f prime and the recipient cell goes from being F -2 f. prime. And so this is uh the conclusion and of our brief introduction to uh f prime cell congregation and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video
5
Problem
Problem
Which of the following statements about bacterial cells and plasmids is false?
A
F- cells do not possess any form of a plasmid.
B
F+ cells possess an F plasmid which is separate from the bacterial chromosome.
C
Hfr cells possess a plasmid that replaces the bacterial chromosome entirely.
D
F' cells possess an F' plasmid which contains plasmid DNA and some bacterial chromosomal DNA.
