Southern Blotting

by Jason Amores Sumpter
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in this video, we're going to begin our lesson on a technique that's called Southern blotting. But before we talk about the actual Southern blotting technique, it's actually first helpful to talk about radioactive probes. And so in this video we're going to focus on radioactive probes. And in our next lesson video, we'll talk more about the Southern blotting technique. And so it's important to know is that after cloning a gene, the DNA that was cloned can actually be used as a probe to detect the same sequence and an unknown DNA sample. And so a probe or probes are really just radioactively labelled molecules that are visualized using radioactive detection. And so DNA probes are going to be single stranded DNA molecules that are going to be complementary to a specific sequence of interest. And so the DNA probe, which is going to be single, stranded and radioactive when it is bound to the specific sequence of interest we can detect the presence of a specific sequence of interest by detecting the presence of the radioactive probe. And so if we take a look at our image down below, we can get a better understanding of these radioactive probes. And so here, in our example saying radioactive probes are used to identify D N A. That is complementary to it in different samples and so noticing this image Over here on the left hand side, we have two different test tubes with different samples. We have sample a over in the left chest tube and sample B over here in the right test tube. And both of these samples contained D N A. And so suppose that we want to identify which of these samples has a specific DNA sequence of interest. What we can do is we can use a radioactive DNA probe, which is going to be a single stranded DNA molecule, as you say here, which is going to be radioactively labelled. And so we can take this radioactive DNA probe and we can put it into both of these samples and under the right conditions. When we incubate the samples with the probe, what will happen is the sample where we can actually detect radio activity is going to have the sequence of interest, whereas the sample where we do not detect radio activity will not have the sequence of interest. And here in this image. The radio activity is represented by the yellow color that you see. And so, in terms of having the sequence of interest because we see radio activity and sample A, we would say that sample A does have the sequence of interest. So we would say yes, here, but sample B, because we do not detect any radio activity would mean that it does not have the sample, the sequence of interest. And so basically, by using these radioactive probes, we can detect the presence of a specific sequence. And so we'll be able to see how radioactive probes are going to be important in the technique. Southern blotting in our next video. But for now, this here concludes our introduction to radioactive probes, and we'll be able to get practice applying these concepts as we move forward. So I'll see you all in our next video