Genetic Impossibility: Female Mule Gives Birth to Foal

by Dr. Hsien-Hsien Lei
Posted July 31, 2007 in DNA in General

Pop Quiz: How many chromosomes do humans have? Horses? Donkeys?

Answer: Humans have 46 chromosomes, horses have 64, and donkeys have 62.

Although that’s an interesting bit of DNA trivia to know, it’s even more interesting in the context of breeding between horses and donkeys. If a horse breeds with a donkey, they end up with sterile offspring that have 63 chrosomes – 32 chromsomes from the horse parent and 31 from from the donkey parent. Horse-donkey offspring aka mules are sterile because their odd number of chromosomes makes it technically difficult for chromosomes to pair up properly during the process of meiosis (cell divison of sperm and eggs). This should mean that mules cannot reproduce.

A female mule in Colorado has beaten insurmountable odds and given birth to a foal . According to Laura and Larry Amos, the owners, there have only been about 50 cases of mules giving birth in the past 200 years and only two have been verified using DNA testing. A previous case of twins born of a mule was made possible by hemiclonal transmission; the father’s chromosomes were silenced and shut down completely. Initial DNA tests on the foal and mother mule-in-question showed that Kate, the female mule, was definitely the mother. Results from a count of the foal’s chromosomes are not yet available. No clue on the possible father.

Mules and More has lots more on Kate and her “Miracle John Mule” including pictures.

HT: Alicia

Tags: genetics, genes, mules, donkeys, foals, dna, animals, weird, bizarre

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4 Comments

Comment by alicia

2007-07-31 23:42:12

You know the other thing I found interesting about this article? Totally unrelated to DNA, but the fact that the owners didn’t even know Kate was pregnant or had a baby until it came peeking around her legs, haha.

Oh, how my mind wanders off topic some, er, most of the time!

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Comment by Hsien

2007-07-31 23:52:45

I thought that was weird too! But I guess stranger things have happened…like those poor teenage girls who just think they’ve gained weight then one day get stomach cramps and find themselves in the bathroom with a new baby.

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Comment by David Bradley

2007-08-01 08:27:58

This is the kind of thing that would sit nicely in some really seedy interspecies, bestially section of the net…it doesn’t bear thinking about.

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Comment by Hsien

2007-08-01 11:15:08

You of the one-track mind.

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