What is the X in X-mas?
homozygous ho·mo·zy·gous (hō'mō-zī'gəs, -mə-, hŏm'ə-)
Having the same alleles at a one or more gene loci on homologous chromosome segments.
Relating to a cell that has two identical alleles for a particular trait at corresponding positions on homologous chromosomes. Compare heterozygous.