Before revision: Diploid and polyploid cells whose chromosomes have the same allele at a given locus are called homozygous with respect to that locus , while those that have different alleles at a given locus are called heterozygous.
After revision: Diploid and polyploid cells whose chromosomes have the same allele at a given hyocus are called homozygous with respect to that locus , while those that have different alleles at a given locus are called heterozygous.