at the most basic level. Some non coding DNA is simply there for structural purposes. We call this constitutive hetero crow Madden and its structural DNA That always remains condensed, and we usually find this around the Centrum year of our chromosome. So this DNA is always gonna stay condensed. It's not going. Thio contain genes so it won't need to be opened up in red. We also find constitutive hetero Crow Mountain at three ends of our chromosomes zones around the telomeres. Now you can have it interspersed in the chromosome, but it's mostly found by the Centrum ear and at the ends. Now we've already talked about another type of non coding DNA and these air segmental duplications. We've talked about thes repeated sequences before, so segmental duplication zehr just segments of DNA that share sequence and occur in more than one place in the genome. And you can see an example of that happening right here where we have this particular area and it gets duplicated. So now we have it twice. Now we have also talked about these short tandem repeats these micro satellites, which are again those short, repeated sequences of DNA that vary between wheels and very number between individuals. So repeated sequences actually are very success susceptible to unequal crossing over which produces mawr repeats. So these repeat sequences are actually self propagating. In a way, you can see an example of them right here. So here we actually have a single nucleotide polymorphism unrelated to what we're talking about. But hey, it's there. We've talked about that before. The focus are these short tandem repeats and you see that we have the sequence C t A. And it gets repeated over and over and over again. And in this one individual he has five repeats another individual as six and another seven and so on and so forth. And some individuals can actually have many, many repeats. I mean big numbers much bigger than you might expect. Now, the reason these air so susceptible toe unequal crossing over, is imagine that you are trying to do some crossing over and you see that you have a sequence match here. C t a c t a and oh, hey, look, there's c t a c t a over there. Well have crossing over between those two points. Boom! You have just created Mawr repeats. So unequal crossing over is really susceptible are, uh, repeated sequences that is, are really susceptible toe unequal crossing over because they have just have the same sequence repeated over and over and over again for a really long stretch of DNA makes it hard for the machinery involved in crossing over to match up the right points on the chromosomes. Now let's flip the page and talk about some other types of non coding DNA.