How do mules reproduce?

Mule is a hybrid of donkey and horse, strong vitality, strong physique, easy to control, can be serviced for 20-30 years, how does the mule reproduce?

How do mules reproduce?

Mules are crossbred by male donkeys and mares, both of which have reproductive isolation and cannot reproduce. The main reason is that mule chromosomes are not paired, germ cells can not divide normally, and basically can not reproduce.

Second, why can't mules have children?

1. Both horse mule and donkey mule have abnormal chromosome numbers, because donkey chromosome 2 is homologous to horse chromosome 1, donkey 13 and horse 11, donkey 14 and horse 13. Donkey 16 and donkey 25 add up to horse 5, and horses have 32 pairs of chromosomes, while donkeys have 31 pairs. Although horses and donkeys are closely related, their gametes can not only combine with each other, but also develop into complete individuals, but the number of chromosomes in their offspring is 32-31, no matter how one chromosome is lonely.

2. But the mule is still lucky, because if this is the number of chromosomes in the cell of a horse (if it is a horse, it is called a monosomic 2n-1), then it basically cannot survive. For diploid species that reproduce sexually, pure haploids are better than this state. On the other hand, if it is the composition of chromosomes in a donkey cell, it becomes trisomy, and the extra chromosome must have three. 32-31 mules are not really 31-to-1 relationships. In other words, during meiosis, it does not simply separate 31 pairs of chromosomes from each other, and then randomly assign the extra one. This is the trouble encountered by mules and even other hybrid animals, whose chromosomes tend to be randomly separated and combined freely in the process of separation. Because for the surviving trisomy, although its fertility is lower than normal, it is also quite high, with the exception of that extra chromosome, the rest can be paired normally and separated from each other.

3. For an unfortunate mule (take the female mule as an example), what is the chance of producing a normal egg, for example, in an extreme case, the egg happens to contain 31 chromosomes from a donkey or 32 chromosomes from a horse. Obviously, this probability is quite low (interested comrades can calculate it), of course, the actual situation does not need to be so extreme, after all, the mule itself can survive, that is to say, it can be a harmonious combination of horse and donkey chromosomes in the egg.