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Expressing cloned genes

Video transcript

- [Voiceover] Normally when we think about cloning, we think about cloning in this sense. So let's say that we've got a baby and it's just so cute that we want two of them. So we can go and clone a baby. Well this isn't exactly what we're talking about when we talk about cloning in a scientific sense. Normally what that means, scientifically is let's say that I've got a cell and there's a certain gene, let's call it gene A for now, and I want to clone that gene. So how do I go about cloning gene A? Well, the first step is to isolate the messenger RNA from the gene of interest. So if we have the messenger RNA, what we need to do is we need to convert it into DNA. So if we add reverse transcriptase, which is an enzyme that will go and actually create DNA from RNA we'll end up with something known as complimentary DNA. Now complimentary DNA, and that's what the C stands for, is basically the complimentary DNA sequence to the MRNA sequence. Now keep in mind that the complimentary DNA only contains exons, so the introns have already been spliced out. We talk about introns and exons in another video. So next, what we have to do is we take this CDNA, this complimentary DNA, and now what we want to do is amplify it. We want to create lots and lots of the complimentary DNA so that we can have plenty of CDNA to work with. In order to do that, we have to take this complimentary CDNA and transform it into a plasmid. Now, what does transform mean? What it basically means is that we're taking the complimentary DNA and we're basically putting it into a plasmid. So we're gonna transform it into a plasmid and this plasmid is going to contain antibiotic-resistant genes. Antibiotic-resistant genes. We'll talk about why that's important in just a second. Now that we have this plasmid, we want to actually infect bacteria with the plasmid. So we want to put it into bacteria. Once it's in the bacteria, what we want to do is we want to actually add antibiotics to the cultured bacteria. So we're gonna add antibiotics and since the plasmid contained antibiotic-resistant genes, the bacteria that were successfully transfected will survive and all the other ones that didn't have the plasmid inserted will die. So now we've got pure cultured bacteria that all contain the plasmid which contains the gene of interest, the DNA of interest, and now the bacteria just does its thing so it's just gonna start to replicate. The bacteria is gonna replicate and as it's replicating, it's gonna produce lots and lots of the gene of interest. It's gonna produce lots of the MRNA of interest. Basically what we just did through this process is we just cloned the gene of interest. And that's what we're talking about when we talk about cloning, at least from a scientific point of view.