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5. Genetics of Bacteria and Viruses

Bacterial Transformation




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Hi in this video I'm gonna be talking about bacterial transformation. So transformation is when a bacterium takes up D. N. A. From the environment. So why or how does DNA get into the environment? Well it can get there in two main ways. One is that it's experimentally placed there. So that means that scientists were doing an experiment and they had a bunch of bacteria and they just threw in some D. N. A. And that you know bacterial liquid. And so now it's just sort of in the culture that that bacterial is growing in. So through experiment told process the second way is a more natural way. And this happens when A D. N. A. D. N. A. When a bacteria dies right it licenses for instance and it can last for a number of reasons it swells and bursts it is just normal death. It has been infected by a virus and now the virus has lISZt it. But essentially um in any of these cases when that happens that DNA that the bacteria had is now released into the environment. And so when it's released it's just floating around in there and other bacteria can dig it up now. Not all bacteria are capable of taking that up. The bacteria that are we call competent and these are the ones that are capable of transformation. So confident bacteria or we call competent cells. They have some kind of physiological stage. So it's natural it can be experimentally induced. Um And this allows for the bacteria to be you know looking for that D. N. A. And able to take it in, right? Because it can't be easy. This bacteria does have a you know a membrane around it. And so that D. N. A. Has to be able to get through that membrane and that's not a normal process. So there has to be some kind of physiological state either high salt or high temperature or something that loosens up that membrane to allow that D. N. A. To get in. And so these are called confidence cells. Now once inside the transfer D. N. A. Can stay in two forms the first time is a plasma. And this is the most common is that the D. N. A. That's found in the environment is a plas bed. And so once it gets into the bacteria it stays a plasma right? And this is the most common experimental approach. So say a scientist wants to grow a gene into a protein, wants to grow a lot protein. What it can do is put it on a plasmid sort of set it with some bacteria. Some competent bacteria induce that bacteria to transform. Take that up and then grow that bacteria. The bacteria will now grow that plasma and produce that protein. So this is a really common experimental approach. Now the other way that it can is that if it's not a plasma it is instead this like double helix say it's just some kind of like chopped up piece of double helix D. N. A. Usually what happens is the bacteria will digest it so it's a single strand and then align it at some point of the bacterial chromosome. Then what's form is a structure called a hetero duplex and there's a single strand and whatever par shin is aligned with. Usually it's it's similarly complimentary it's not perfect but it's close enough that it aligned and it will form this hetero duplex process. So what this looks like is if it's a plasma you can see it's just transformed and it's taken up by the cell. If it's a devil stranded you can see that it enters the cell. It's digested to a single strand and then it aligned to the complementary region in the bacterial D. N. A. This forms that hetero duplex Now transformation can also be used to map genes. So here we are back to mapping determine where the gene lo chi are. So what happens is you can induce some kind of fragmentation of the D. N. A. And you can do this through D. N. A. Extraction or certain enzymes or you know temperatures or salt concentrations. There's lots of ways to introduce fragmented D. N. A. Right? So if you have D. N. A. You want to know where the genes are located on it chop it into a lot of pieces incubate it with some bacteria and some competent bacteria and then allow for transformation to take place. Now the closer the two genes are together the more likely they'll be taken up together because it'll be less likely that there's they've been chopped up in between the genes. Whereas the farther they way the way the genes are the less likely it is they'll be taken up together. So it's called double transformation when jeans two genes are taken up together. So this is what this looks like. So here we have some jeans red and a blue jean that we're interested of mapping. We want to know how close they are together. So in this case they're close together in this case they're farther apart. Now we do something to this DNA to chop it into a lot of pieces. Like I said before there's lots of different ways to do this. It doesn't matter which way you choose. But you chop the D. N. A. To a lot of pieces. So now we have our fragment of D. N. A. And you can see that the genes that are close together remain close together right? There was nothing that chopped them up in between there where the genes that are farther apart actually ended up being chopped separately. And so they're they're two completely different fragments. And so when transformation happens the genes that are close together will be picked up together because they were they were never cut apart from each other. Whereas the genes and so this would be the devil transformation. And so the genes that are farther apart have been chopped up in between them. And so now you get only one of the genes um incorporating. So this process here is what allows us to map genes via transformation. So transformation is awesome. It's a huge experimental technique. If you ever plan on working in a lab, you'll do it at least once. Um So important to know with that, let's now move on.

Transformation is the process of what occurring with DNA?


Scientists must use what type of cells to transform DNA in the laboratory?


The DNA from a bacterium with the genotype a+ b+ c+ is used to transform a bacteria with the genotype a b c. Gene pairs were checked for cotransformation with the following results. Using these results determine which genes are linked.