why are mules infertile? If a horse and a donkey have close enough genetics to have offspring, why is that offspring left with genetics that render them unable to have their own offspring?

Question

why are mules infertile? If a horse and a donkey have close enough genetics to have offspring, why is that offspring left with genetics that render them unable to have their own offspring?

In: 8368

Answer 1

Basically, it’s because of chromosomes.

Horses have 64 chromosomes

Donkeys have 62 chromosomes

When you make a baby, half the chromosomes come from mom, half come from dad.

If 2 horses have a baby, 32 chromosomes come from each parent. So the baby gets 32+32=64 chromosomes. Perfect.

If 2 donkeys have a baby, 31 chromosomes come from each parent. So the baby gets 31+31=62 chromosomes. Perfect.

But if a horse and a donkey have a baby… Well, horse parent gives 32, and donkey parent gives 31… That baby is left with 63 chromosomes.

If mules have 63 chromosomes, that is a problem, because you can’t split that in half. If a mule tries to have a kid, the chromosomes won’t line up correctly, and the fetus won’t start to develop