👉 Heterozygosity refers to a situation where two individuals have one allele (a gene) that is expressed in both of their respective cells. This means that when you look at an individual, they can be either homozygous or heterozygous for the same gene. For example, if someone has a trait that affects their eyesight and also has a trait affecting their hair color, they are considered heterozygous because both of their eyes have this trait and their hair colors