Androgen insensitivity syndrome 1


Good news!

Your horse is clear of this gene mutation for androgen insensitivity syndrome.

Your horse cannot pass on this mutation.

There are no breeding implications.

What is Androgen Insensitivity Syndrome?

An inheritable condition that prevents masculinization of the foal at the time of conception, during embryo development and after birth. Affected horses appear to be female but are infertile and have high levels of testosterone in their bodies. Often these horses will display stallion-like behavior around other horses.

Genomic Details

Androgen insensitivity syndrome is caused by a mutation in the AR gene on the X chromosome. There are four known mutations for this disease that are in slightly different positions on the gene. Each mutation can influence the development of androgen insensitivity syndrome depending on breed. The AR gene is responsible for giving instructions on how the horse’s body responds to naturally occurring male hormones. Horses with the mutation are genetically male yet have female characteristics. They are also sterile.

The mutation that causes androgen insensitivity syndrome is a switch in one of the four base pairs that make up a DNA molecule. Cytosine (C) is replaced by Thymine (T) changing the AR gene. Therefore, a horse’s genetic result for hydrocephalus is one of three possibilities:

  1. C/C: Normal. Does not have the disease. Does not have the mutation.
  2. C/T: Carrier. Does not have the disease. Carries one gene mutation from one parent. This might be passed to their foal. This is the result for your horse.
  3. T/T: Affected. Has the genetic disease. The horse has inherited a gene mutation from each parent. One mutation will be passed to their foal.