Everything Horses and Livestock® Magazine Sept 2018 Vol 3 Issue 3

Everything Horses and Livestock Magazine ®

Our Featured Writer: Brandy Von Holton

The Simple Genetics of a Mule

Every species has a specific number of chromosomes. Chromosomes are that specific organism’s genetic combination between each parent. Every living creature has genetic information which is called DNA. Not only animals, but plants do, too. Black Mulberry’s have 308 chromosomes, carrots have 18, bats have 44, asparagus have 30, earthworms have 36, humans have 46, horses have 64, and donkeys have 62. Now there are exceptions to the rules everywhere. There is a subspecies of horse called a Przewalski’s Horse that is native to central Asia that has 66 chromosomes. Zebras have between 32 and 46 chromosomes depending upon the species. Chromosome number counts can change a couple of different ways. Sometimes miracles happen and children with Down Syndrome are born with a chromosome number count of 47. Sometimes hybrids can occur if species are so closely related that their species can mate. This is the exact case

with a mule.

also has a chromosome number count of 63, just as a mule. However, the role of the horse and donkey are reversed. A hinny is a combination of a female donkey, a jenny, and a male horse, a stallion. With a mule and a hinny having 63 chromosomes, that number cannot be evenly divided into whole numbers which is needed in sexual reproduction. This is the reason mules and hinnies are sterile. Even though they are sterile, a female still comes into heat and a male can be gelded. Even though mules are sterile, chromosomal

A horse has 64 chromosomes, but only half of those chromosomes will be passed on to their offspring. This means that the egg from the fertile mare has 32 chromosomes. A donkey has 62 chromosomes, but only half of those chromosomes will be passed to their offspring. This means that the sperm from the fertile male donkey, a jack, has 31 chromosomes. When the 32 chromosomes and the 31 chromosomes combine, a mule is created with a chromosome number count of 63. A hinny

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