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.
Xyy redirects here. For the CIE XyY colour model, see XyY. XYY syndrome is a genetic condition in which a human male has an extra male (Y) chromosome, giving a total of 47 chromosomes instead of the more usual 46. This produces a 47,XYY karyotype, which occurs every 1 in 1,000 male births.or the CIE XyY colour model, see XyY. XYY syndrome is a genetic condition in which a human male has an extra male (Y) chromosome, giving a total of 47 chromosomes instead of the more usual 46. This produces a 47,XYY karyotype, which occurs every 1 in 1,000 male births.