Compatibility is when the genes that cause the disease are on the sex chromosomes. Specifically, there are 23 pairs of chromosomes, 22 of which are autosomes and 1 pair of which is a sex chromosome, and if the sex chromosome is XX, the person is female, and if it is XY, the person is male. If the disease-causing gene is on the X or Y chromosome and is passed on to the next generation, it causes a hereditary disease, which is called companion inheritance. Some of the more common forms are hemophilia, color blindness, and myotonic dystrophy. If the trait is dominant, the offspring will develop the disease if one of the two chromosomes or two of the two chromosomes carry the gene. If it is a recessive form of consanguineous inheritance, a female must have the gene on both chromosomes to develop the disease, and in the case of a male, the disease may develop if the consanguineous gene is present on one chromosome.