Originally Posted by jaida
Well, from my memory (for what's worth) I thought that each parent gives up half of their chromosomes during meiosis. And if that's true, then in this case, what happens to the extra chromosome of the horse? For some odd reason, I had it in my head that in order to mate, the parents need to have the same amount of chromosomes. Guess that's not the case.
Keep in mind that when you say 64 chromosomes...that is 32 pairs
chromsomes. In other words, you have a "double genome". So during meiosis, it is the pairs
of chromosomes that are being split up, so there isn't any leftover. Meiosis produces gametes, which have only one set of each chromosome/genome. Gametes then join during fertilization to produce an organism that is once again a double genome, 32 pairs of chromosomes (64 total)...one set from mom, one set from Dad.
In the case of mules/hinny....its a joining of a two gametes that have a different number of chromosome (one gamate has 32, the other 31...when joined, a total of 63). The extra horse chromosome does not have a "mate" donated from the donkey but it still leads to a viable embryo (moste times in biology an unpaired chromosome means the embryo will not be viable). However, this may be why the resulting offspring (mule/hinny) is not able to reproduce.
Hope this helps...