When we say that an individual is <u>heterozygous</u>, it means that the two alleles at the locus we are studying are different from one another. That is, each one of the parents contributed a different allele.
On the other hand, If the alleles at that locus were the same we would say the individual is <u>homozygous</u>. In other words, the two parents contributed each the same type of allele.
