So translocations pretty much describe when a chromosomal segment is moved to a different chromosome. This can be, they can actually just switch parts, so two completely separate chromosomes can switch parts, or just one can move to the other. But it's essentially that chromosome being moved to a different location or translocation. Now there are two types. The first type we're going to talk about is reciprocal translocations. And these are when two chromosomes trade acentric fragments. First, do you remember what acentric means? Right? It means without a centromere. So this is a fragment that does not contain a centromere in it. And there are three ways that these translocations are sorted into gametes because the reason we study these is that they're inherited or they can be. And so, when we think about translocations happening, it's important to understand how that happens, but that's easy enough to conceptualize. Right? It's a portion of a chromosome without a centromere is switched with another portion of a chromosome without a centromere. But that doesn't necessarily do anything unless it's inherited, and so when we talk about these chromosomal aberrations and mutations, we have to talk about them in terms of gametes, of how they're inherited. So whenever this translocation occurs, the way that they're sorted into gametes can be classified in three ways. So when I talk about these, I'm going to talk about the normal chromosomes and the translocated chromosomes. So the first one, if it doesn't make sense, I'm going to go over a really detailed image of this, so just hold on.

We have adjacent one segregation, and this is when the gametes formed have one normal and one translocated. And notice the numbers here because you start out with two chromosomes. Here we go. And if these two change spots, then you have a normal one, a translocated one, a normal two, and a translocated two. Right? Because these two are the ones that underwent translocation. And the numbers actually matter because in one situation you're referring to homologous chromosomes, and in another, you're referring to nonhomologous chromosomes. And if it doesn't make sense, there's an image to explain it, but just sort of know that these are how the niamites form in adjacent one segregation, and these are inviable. Adjacent two segregation is the same thing, but notice the numbers here are different. You have one normal and one translocation, but these are homologous, whereas these are not homologous, and but they're both inviable because you don't have one full set of chromosomes. And then you have alternative segregation, and these you have one set of gametes that are both translocated and one set that are normal, and so the gametes are all viable. Let's walk through an example of this.

So like I said, we start out with chromosomes. We have normal one, normal two, and a type of translocation has occurred here. Right here and here. So now we have a translocated one where this is a, b, g, and h. We have a translocated two with e, f, c, and d. And these are marked by their the letters. So the letters are representing different genes in this case. We have one chromosome that has a, b, c, or d. We have another that has e, f, g, and h, and these are two separate chromosomes. These are not homologous. Right? Because they have different genes on them. Anything with an a, b, c, or d is homologous, but these are actually two separate chromosomes, chromosome one and chromosome two. And so there's a homologous pair. Right? So if we were drawing these, like how they how we normally see them, you would see them like this. And I guess this is supposed to be red. Hold on. E f g h e f g h. So these are the homologous pairs, each one of these. But the black and the red are two different chromosomes. But in this case, a translocation has occurred here. Right? These two have switched over, and these two have switched over. So now you get a normal one, n 2, two normal chromosomes. Right? This one here and this one here. And you have two translocated ones, the ones that translocated here, and the ones that translocated here. And this is important. So now, when you get the gamete, or you get the cell, essentially, what happens is this is what you have. You have one normal, this is an n one, and you have two normals n 2, and you have your translocated t 1 and t 2.