What is the designation of a mare's sex chromosome pair?

The designation of a mare's sex chromosome pair is represented by XX. This is characteristic of female mammals, including horses. Each female inherits an X chromosome from each parent, which determines her sex as a mare.

In horses, the male sex chromosomes are designated as XY, indicating one X chromosome from the mare and one Y chromosome from the stallion, which results in a male foal. The ZZ designation is typically associated with certain bird species and does not apply to horses. Similarly, the YY combination cannot exist in typical diploid organisms, as there are no known viable embryos with two Y chromosomes in mammals. Thus, the pairing of chromosomes designated as XX is specific for females, confirming that a mare possesses this pairing.