The bottom line is, in the racing world, a âniceâ horse is not as important as a âwinningâ horse. Below: Mountain Horses must be certified for both gait and temperment before breeding, to ensure the best traits get passed on to the next generation.
Exceptions to these generalisations happen in the cases of XX males or XY females, or other syndromes. This system is in contrast with the ZW sex-determination system found in birds, some insects, many reptiles, and other animals, in which the heterogametic sex is female.
Because in males they have only 1 X chromosome. The other one is Y. But in females they have 2 XX chromosomes so the chance that X chromosome will carry disease to cause illn â¦ ess is lower. Example: lets say xx (recesssive) phenotype makes illness, whereas XX (dominant) is healthy.