Genetics 101: Cross talk

By guest blogger Leslie Johnstone

What do you get when you cross a horse with a donkey? It depends!

A mule, like this one, results from crossing a horse and a donkey.

When a male donkey is crossed with a female horse, the resulting offspring is a mule. If a male horse is crossed with a female donkey, then the baby is called a hinny. Hinnies are much less common and tend to be smaller than mules and look more like horses.

Horses are half of the equation that makes a mule or a hinny.

When two different species of animal, such as horses and donkeys, are bred, the offspring are called hybrids. Both donkeys and hinnies are hybrids. Donkeys have 62 chromosomes in their cells, but horses have 64. Mules and hinnies both have 63 chromosomes, being  a blend of both parents.

Mules and hinnies can't be successfully bred to other mules and hinnies, but there have been some cases of female mules giving birth to babies sired by horses or by donkeys.

The other half of the equation is a donkey, like this one.

Mules are usually very smart, strong animals and are used as pets, for transportation, and for farming. They have harder hooves and stronger coats than either of their parents. Mules and hinnies are also generally longer living than their parents and more resistant to diseases.

Leslie Johnstone and her writing partner, Shar Levine, are co-authors of dozens of fun practical-science books for kids. Leslie took the photos appearing with this post.