Concept 5: Individuals can be homozygous or heterozygous.
Homo means same and hetero means different. Zygous stands for zygote. If genes are in pairs in somatic cells and genes can have alleles, different genetic combinations can occur. An individual can have two copies of the same allele (homozygotes AA or aa) or they can have two different alleles (heterozygote Aa) (Fig. 8). The genetic makeup of an individual at specific gene pairs is called the genotype.
Figure 8. A somatic cell from an individual who is heterozygous at the B,b gene pair and homozygous at the A gene pair. (Image by P. Hain)