 So let's do look at an example of how aneuploidy happens. And again, I mean, it's just shocking how DNA, protein synthesis, meiosis and mitosis, all of them tie into concepts in heredity. You can't separate them. So remind yourself, push pause and do this task. Go through and draw a picture of this cell right here with two different chromosomes. So it's a diploid cell with two different chromosomes. Draw that cell in each of these phases and then draw of meiosis and then draw the resulting gametes. And now that you've done that, because I know you did it, let's go ahead and go through that together what the answers are. So if you were to go put this cell in metaphase, you can see that we would line up our homologues. They hook up in prophase one and in metaphase one, the homologues line up on the metaphase plate. Think about independent assortment. We could flip-flop those puppies and end up with a different set of resulting gametes. But in anaphase one, we're going to separate them. Just pretend like all I did was I'm going to make the rest of the phases just happen instantaneously. I've got two cells now. Did you see that leap? I'm just making this into a cell and I'm making this into a cell. Now I've got two cells that are in metaphase two where the sisters line up on the metaphase plate. And then anaphase two where the sisters are split apart and these are all my resulting gametes. Does that work for you? Now if all of that was like done, been there, done that a million times, meiosis, I got this, then contemplating nondisjunction during meiosis one should be pretty straightforward and you could draw the whole thing again. So metaphase one is going to look exactly the same whether nondisjunction happens or not. Remember this is saying specifically nondisjunction is going to happen in meiosis one. That means that my homologs are not going to split apart. So anaphase one, look, my big homologs didn't split. That's straight up a mistake. That's not cool. But now look what happens in metaphase two. I've got one cell that only has one chromosome and I've got one that actually has three. But remember in metaphase two, my sisters are going to split. My homologs aren't lining up anymore. And in anaphase two, everybody's sisters split and look at my resulting gametes. This guy has two copies already of the big chromosome. So when it combines with an egg that has its own copy of the big chromosome, you're going to end up with nondisjunction or aneuploidy. You're going to end up with three big chromosomes. You combine this with a normal egg and you're going to end up with just one chromosome instead of two. So both of those are examples of aneuploidy. Now the next thing we have to look at is, okay, what's it going to look like if nondisjunction happens in meiosis two? That's going to be a different situation. So meiosis one is normal. Meiosis two, metaphase two is normal, and anaphase two doesn't happen right. And now we end up with just two gametes that are wonkadoosy instead of all four of them being wonkadoosy. That's just an example. That's like a visual of how this actually happens. And again, understanding meiosis helps you just use this as like, dude, all it is is an application and not a problem, not something you have to memorize, and you need to understand meiosis to start this out. Okay, now let's look at some pedigrees.