Okay. So now, let's talk more specifically about autopolyploidy. Autopolyploidy typically results in triploids. Not always, but most often, they are triploids. Usually, autopolyploid individuals are sterile. This is because their gametes will receive either 2 or 1 chromosome from each pair. Let's visualize this: they're typically triploid, so they have one chromosome here that's triploid, one here that's triploid, and one here that's triploid. When this undergoes meiosis to create these gametes, what happens is that some of the daughter cells will actually end up with 2 copies, and others of the daughter cells will end up with one copy. Because they started out with 3, it's very unlikely that only one cell will get all 2. Usually, what will happen is that it'll get 1 here and 2 here and maybe 2 here and 1 here, so you end up with this mix where some of the chromosomes have 2 copies and some of them have 1. This creates a gamete that is just not viable. So when it undergoes fertilization with a normal gamete, sometimes it's going to have some triploid, it's going to have some that end up as diploid, and it's just going to be very confusing. Right? And so the gamete typically doesn't survive, and typically, autopolyploids are sterile.
Whenever there are mixed numbers of chromosome sets, so some chromosomes have 2 copies, some have 1, some have 3, this is called aneuploidy, and we're going to be talking about this a lot. Remember, you can go back to the previous video; this was one of the different types of chromosome mutations, the one we're not talking about yet. But, this is when you have a mixture of diploid and haploid chromosomes or can even be triploid. Right? Any kind of unusual mixture of a chromosome set, because not all of these triploids here will segregate equally. Right? There are 3 of them, so sometimes 2 will go to one, and sometimes one will go to another.
There are many classes of autopolyploids. You have monoploids, which use a haploid cell meant for fertilization as an embryo. We talked about this before with the bees and the wasp. This is the organism that develops from parthenogenesis. You can have autotriploids, which are triploid for each set. An example of this is bananas; if they have 40 chromosomes, all 40 of them have 3 copies. And you can also have autotetraploids, which again, are 4n (where "n" refers to the basic number of chromosomes), indicated by 'tetra' for four. We can sometimes see this in plants such as crops or even large flowers, because typically, this results in a larger size. Autopolyploidy often results in larger size because you have the entire chromosome set having multiple copies. And so, in the organisms that can survive with that, which is kind of rare, but in the organisms that can, they are typically just bigger organisms. They have extra chromosomes, they are producing extra of every gene they have, and if they can survive doing that, which some plants and some amphibians can, they are typically just bigger organisms. Very common.
So here are examples: you have a monoploid, where that one chromosome is used as an embryo without fertilization. Here's an autotriploid where you have 3 copies of every set; we've seen this before, but essentially, that's the example. So this is the autopolyploidy. So with that, let's turn the page.
