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Name: Amy
Status: Student
Age: 17
Location: N/A
Country: USA
Date: 2000-2001

Why are mules and hinnies sterile?

Mules and hinnies are crossbred between 2 species: donkeys which have 62 chromosomes and horses which have 64 chromosomes. Donkey and horse chromosomes also differ slightly in structure. Mules and hinnies have 63 chromosomes that are a mixture of one from each parent. This prevents the chromosomes from pairing up properly and creating successful embryos. While this is generally true, there are a few reports of fertile mules and hinnies.

Laura Hungerford, DVM, MPH, PhD
University of Nebraska

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