Last Updated on January 8, 2022
The world of genetics is a fascinating subject, and one which many horse fans are interested in! Chromosomes are an integral part of this process and help to pass on DNA from parents to offspring. But how many chromosomes do horses have?
If you’ve ever wondered how genetic traits are carried from a dam and sire to their foals, then you have chromosomes to thank for this. Let’s take a look into the world of equine genetics and find out how many chromosomes horses have!
What Is A Chromosome?
Chromosomes are very tiny structures located inside the nucleus of almost all animal and plant cells. They resemble tiny threads and carry genetic information in a molecule called deoxyribonucleic acid (DNA). Each chromosome is made from protein and a single molecule of DNA.
DNA is an incredible molecule that contains instructions for cell division and replication. This information is what makes each type of living creature unique. This information is passed from parents to offspring and is also passed on when new cells are created.
So, essentially chromosomes and DNA are a unique code, that determines everything about the appearance of an animal or plant. Within each chromosome are hundreds or thousands of structures called genes.
Each gene carries instructions for making specific proteins. When a new cell is created, the chromosomes pass on these instructions.
What Do Chromosomes Do?
It is easiest to think of chromosomes as information storage and management system!
Firstly they keep DNA tightly wrapped around histones – these are spool-like proteins contained within the chromosome. This neat packaging system means that tiny individual cells can each contain a huge amount of information.
Chromosomes are also a vital part of ensuring that DNA is accurately copied when new cells are created.
How Many Chromosomes Do Horses Have?
When counting the number of chromosomes, they are most commonly referred to in pairs. This is because each pair of chromosomes contains one from the female parent and one from the male. These two chromosomes work together to determine the particular characteristics of their offspring.
so how many chromosomes do horses have? A horse has 64 chromosomes in total, which is 32 pairs. So, it gets 32 chromosomes from its dam, and 32 from its sire. Each of the 32 chromosomes is matched, so they contain the same type of information.
This is why a horse will inherit some traits from its sire, and some from the dam. In the horse, the chromosomes determine everything about the appearance, characteristics, and nature of the horse. This will include the coat color, height, stature, and thousands of other characteristics.
The way that the gender of the horse is determined is also due to chromosomes. A mare has 2 X chromosomes, and the stallion has 1 X and 1 Y chromosome. The mare gives an X chromosome to the foal, and the stallion either an X or a Y chromosome.
If the stallion gives a Y chromosome, the foal will be male. If he gives an X chromosome, the offspring will be female.
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Does The Horse Chromosome Number Ever Change?
The number of chromosomes in a horse is always 32 pairs, so a total of 64 chromosomes. However, there are some variations in the number of chromosomes in other equine species!
Donkeys have 62 chromosomes, so have one less pair than a horse. Different species of zebra have far fewer chromosomes, with mountain zebras having just 32 chromosomes.
Interestingly, it is possible to interbreed horses with donkeys or zebras. But what happens when you breed two animals with different numbers of chromosomes?
The best example of this is when you breed a male horse with a donkey. This will give you one of two combinations:
- A male horse and a female donkey produce a hinny
- A female horse and a male donkey produce a mule.
Mules and hinnies have been bred and used for centuries, as they make versatile and strong working animals. However, mules and hinnies cannot have offspring of their own. But why is this?
Hinnies and mules do not produce sperm or eggs and are reproductively sterile. This is because their chromosomes do not match up, and they also have an odd number of chromosomes.
A mule or hinny will get 32 chromosomes from the horse parent, and 31 from the donkey parent. The result is a total of 63 chromosomes, which do not match up into pairs!
It is not just the odd number that is the problem, but also how they match up. If they had chromosomes from two horse parents, each pair would be a perfect match, with the same type of information. However, the horse and donkey chromosomes have very slight differences, and this causes problems when it comes to producing offspring.
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Why Is Horse DNA Important?
Breeders of horses are very interested in the DNA of horses, as they can use this information to breed foals with certain desirable traits. A sire or dam is often referred to as having ‘strong genes’, meaning that their offspring take on more of their characteristics than the other parent horse.
So, if we want to breed horses that are a certain color, or that can run faster, or that are smaller in size, then we select parents that will give a greater chance of passing on these traits. This is why the top racing stallions are often retired to stud at a young age, as their genes are highly sought after!
DNA is also important for verifying the bloodlines of a horse. Some breed societies ask for foals to be DNA tested when they are registered, to maintain the purity of the breed.
The other important function of DNA testing in horses is to screen for horses susceptible to hereditary diseases. This means that breeders can select horses free from genetic mutations that may cause health problems, with the aim of eliminating these diseases from the bloodlines altogether.
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Summary- How Many Chromosomes Does A Horse Have?
So, as we have discovered, the chromosomes of a horse help to pass on genetic information when cells replicate. A horse has 32 pairs of chromosomes, which is 64 in total. A donkey has one less pair than a horse, and zebras have even fewer.
We’d love to hear your thoughts on horse chromosomes. Are you amazed at the amount of information that these tiny structures contain? Or maybe you have some questions about horse genetics? Please add your comments below and we’ll get back to you!
Kate Chalmers is a qualified veterinary nurse who has specialized in horse
care for the vast majority of her career. She has been around horses since
she was a child, starting out riding ponies and helping out at the local
stables before going on to college to study Horse Care & Management. She
has backed and trained many horses during her lifetime and competed in
various equestrian sports at different levels.
After Kate qualified as a veterinary nurse, she provided nursing care to the
patients of a large equine veterinary hospital for many years. She then went
on to teach horse care and veterinary nursing at one of the top colleges in
the country. This has led to an in-depth knowledge of the care needs of
horses and their various medical ailments, as well as a life-long passion for
educating horse owners on how to provide the best possible care for their
Kate Chalmers BSc (Hons) CVN, Dip AVN (Equine) Dip HE CVN REVN RVN A1