If an organism is homozygous for a particular trait, the organism A. has extra alleles on both chromosomes in a chromosome pair. B. is missing alleles on the chromosomes in a chromosome pair. C. has different alleles on the chromosomes in a chromosome pair. D. has the same allele on both chromosomes in a chromosome pair.
If an organism has two copies of the same allele, for example AA or aa, it is homozygous for that trait. If the organism has one copy of two different alleles, for example Aa, it is heterozygous.
