in this video we're going to begin our lesson on horizontal gene transfer. And so recall from our previous lesson videos that horizontal gene transfer is going to occur between two organisms that are not direct descendants of one another. And so these two organisms are going to be transferring genes between each other. And so horizontal gene transfer allows cells to quickly acquire new traits. And it also drives genetic diversity among organisms. Now there are three known mechanisms of horizontal gene transfer in bacteria. And notice that we have those three mechanisms number down below 12 and three. The first mechanism is transformation. The second mechanism is trans diction. And the third mechanism of horizontal gene transfer is conjugation. And so what you'll notice is that these numbers that you see here also correspond with the numbers that you see down below in our image. And so for the first mechanism of horizontal gene transfer. Again we have transformation and transformation is horizontal gene transfer via the uptake of free or naked D. N. A. In the environment by a cell. And so if we take a look at our image down below at number one. Over here on the left hand side notice it's showing you transformation. And so transformation is when a cell is able to bring in free or naked DNA from the environment. And so when the free or naked D. N. A. Is brought into the cell and incorporated into the cell then we refer to this as transformation. And later in our course will be able to talk more details about transformation transaction is again going to be a form of horizontal gene transfer and it's going to occur between cells and it's going to be mediated specifically by a bacteria fage virus. And so a bacteria fage is a specific type of virus that is going to infect bacteria. And so if we take a look at number two down below notice that this is showing us transducer action which again is not to be confused with transformation because they kind of sound similar but they are different. And so what you'll notice here is that it is showing you a bacteria fage or just a fage for short. And the bacteria fage is going to be responsible for transferring D. N. A. Into the cell. And so you can see that donor cell D. N. A. Is being transferred by the bacteria fage and then the recipient can receive that D. N. A. And again we'll get to talk more about trans direction later in our course this is just the introduction to it. And then the third and final mechanism of horizontal gene transfer is conjugation. And this one here is referring to the direct horizontal DNA transfer between cells during direct cell to cell contact. And so notice that the final image over here is focusing on conjugation. And so what you'll notice is that we have to neighboring cells and they end up forming direct cell to cell contact. Where DNA and genes can be transferred from one organism over to a neighboring organism. And so notice that the green molecule originally was not over here in this cell on the right. But now at the end both cells have the green molecule. And so this is an example of conjugation, the transfer of genes via direct cell to cell contact. And again, we'll be able to talk more about conjugation later in our course. This is just the introduction. And so you can see that this is really our map of our lesson on horizontal gene transfer. And moving forward. We'll get to talk more about each of these mechanisms of horizontal gene transfer in more detail. Starting with transformation. Then we'll move on to transaction and last but not least, we'll move onto congregation. And so this concludes our brief intro to horizontal gene transfer. And I'll see you all in our next video.

in this video, we're going to talk about the fates of horizontally transferred D. N. A. Or in other words we're going to talk about what happens to the D. N. A. That is horizontally transferred into an organism. And so following horizontal gene transfer really there are three possible fates of the D. N. A. And so we're showing you these three possible fates down below in this image. And so what you'll notice is at the top, what we're showing you is a bacterial cell. And in the blue that you see over here, what we have is the chromosome all D. N. A. And this represents the original DNA. That belongs to the bacteria. And then on the right what we're showing you is horizontally transferred D. N. A. This is the DNA. That is going to be obtained by the cell via horizontal gene transfer. And so this horizontally transferred DNA can have one of three fates in the cell. And those three fates are once again down below the first fate is that the horizontally transferred DNA is integrated into the chromosome? Uh and it replicates alongside the chromosome. And so what can happen is this horizontally transferred DNA can integrate and become a part of the chromosome of D. N. A. And so that is what we are seeing down here is the integration of that horizontally transferred DNA. So that's one fate. The second fate is that the horizontally transferred DNA remains self replicating without actually integrating into the chromosome. And an example of this would be a plasmid which is a small circular um extra chromosome will segment of DNA. Okay. It's separate from the chromosome and it is self replicating. It can replicate on its own without having to integrate. And so that is another option for the horizontally transfer D. N. A. And then the third possible fate for the horizontally transferred D. N. A. Is that it is actually degraded. And the degraded horizontally transferred D. N. A. Is going to end up having no effect. And so if the cell degrades it into a bunch of pieces like this eventually this is going to end up having no effect on the silk. And so really what we're saying is that only options one and two which are integration of the D. N. A. Or self replicating um DNA. Is going to stabilize the transfer gene within the population and allow this bacteria to basically pass on those genes to future generations as it replicates. And so um these are some important fates to keep in mind about this horizontally transferred DNA as we move forward. And so that concludes this video and I'll see you all in our next one

in this video we're going to briefly discuss the integration of D. N. A. Via homologous recombination. And so homologous recombination is really just referring to the process of the genetic exchange between two similar strands of DNA. And so homologous recombination allows molecules to integrate into other segments of DNA. And so homologous recombination can only occur if the donor DNA actually has a similar nucleotide sequence to the recipient cells chromosome. And so if we take a look at our image down below we can get a better understanding of homologous recombination. And so what you'll notice is on the left, we're showing you the chromosome all D. N. A. Of say the bacteria. And so again the chromosome will D. N. A. Is the original DNA that's found in the bacteria. And down below what we're showing you is the donor DNA. That could have potentially been obtained through horizontal gene transfer. And so what you'll notice is that the donor DNA has some regions here in or highlighted an orange that have similar sequences to the chromosomal DNA. And so these yellow highlighted regions represent regions that have uh similarity. And so when these regions have similarity it creates the possibility for homologous recombination. And so what can happen is the donor DNA which I'll highlight here like this can be incorporated and replace the chromosomal DNA at this region. And so the chromosomal DNA can be removed whereas the donor DNA can be integrated. And so really this is what we are seeing here. The donor DNA can be integrated into the chromosomal DNA. And it replaces a region of the chromosomal DNA. And so this is what we call homologous recombination. And again it can allow uh donor D. N. A. To be incorporated and integrated into the chromosomal DNA. And so this year concludes our brief lesson on the integration of DNA via homologous recombination. And so we'll be able to get some practice applying this as we move forward. So I'll see you all in our next video.