To determine which genotypes are heterozygous, we first need to understand what heterozygous means. A genotype is considered heterozygous when it consists of two different alleles for a given gene, represented as ‘Aa’. In contrast, a genotype is homozygous if it has two identical alleles, such as ‘AA’ or ‘aa’.
Now, let’s analyze the provided genotypes:
- 1. aa: This is homozygous because both alleles are the same.
- 2. tt: This is also homozygous, with both alleles being identical.
- 3. aa: Like the first, this is homozygous.
- 4. qq: This is again homozygous since both alleles are the same.
- 5. aa: Once more, this is homozygous.
Based on this analysis, none of the genotypes provided (aa, tt, aa, qq, aa) are heterozygous. All of them are homozygous.