DNA Methylation

by Jason Amores Sumpter
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in this video, we're going to introduce another type of eukaryotic chromosome modification, which is DNA methylation. And so, in addition to histone modifications like his stone assimilation and histone d oscillation, the actual DNA sequence, not just the headstones can also be chemically modified to regulate transcription. And the most common DNA modification is methylation and methylation is really just the process of adding a methyl group or a CH three group, uh, to another substance. And typically, when it comes to DNA methylation, it turns out that the nucleotides side a scene are the ones that are most susceptible to methylation. And so the cytosine residues are the ones that are going to be methylated. Now, DNA methylation is a way to prevent transcription by blocking RNA. Polymerase is access to the promoter, and so DNA methylation will turn off a gene or turn off transcription. And so, in our image down below, we can see in our example that methylation of cytosine nucleotides is going to block transcription and turn off a gene. And so what you'll notice is over here on the left hand side, notice that we have a C dilated histone modifications. The stars the Green stars from our last lesson video represent assimilation and assimilation we know is going to turn on genes. So jeans are going to be turned on by assimilation because the DNA is going to take a U chromosome state and that is going to promote transcription. And so the genes turned on by assimilation by promoting transcription. And so the RNA preliminaries will be able to bind to this open and available D N A. And we'll be able to transcribe genes in this DNA that is available here. And so this is a way of turning on the gene, however, however methylation of specific cytosine residues, cytosine, nucleotides, uh, methylation of cytosine, which methylation is being adding a ch three groups to the molecule. It's going to be represented using one of these red Star shapes, uh, noticed that the D N A itself can actually be methylated. And so this modification occurs to the DNA sequence directly not to the headstones. And so the DNA can be methylated, and the DNA methylation is a way to turn the gene off. The genes are going to be turned off and notice that the methylation is blocking RNA preliminaries from binding to the DNA. And so the RNA preliminaries will not be able to transcribe the D. N. A. And the gene is being turned off through methylation of cytosine nucleotides. And so what you can see here is that through assimilation and methylation, the eukaryotic organisms have a very, uh, complex way to be able to regulate their genes, turn the jeans off and turn the jeans on, depending on the type of modification that's made. And so this here concludes our introduction to DNA methylation, 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.