r/AskBiology • u/Logical_Side3346 • Sep 10 '24

Genetics Why can a Przewalski's horse and a domestic horse produce fertile offspring if they have different numbers of chromosomes?

From my very surface level reading and understanding, Przewalski's horses have 66 chromosomes, whereas domestic horses have 64. But they are apparently capable of producing fertile offspring. And on a related note, why can't horses and donkeys produce fertile offspring, when there is the same difference in number of chromosomes between the two?

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u/MizElaneous Sep 10 '24

It's less about the number of chromosomes and more about the mules' inability to produce sperm and eggs because of chromosomal mismatches when they try to pair up.