How many total combinations of alleles can arise from two heterozygous parents?

When considering two heterozygous parents, each parent carries two different alleles for a particular gene. For instance, if we use the alleles A and a, a heterozygous parent would have the genotype Aa. When two heterozygous parents mate, the possible combinations of alleles that can arise in their offspring can be determined using a Punnett square.

Each parent provides one allele to the offspring. The possible alleles from each parent are A and a. When the alleles from one parent are crossed with those from the other, the combinations are as follows:

1. A from the first parent with A from the second parent results in AA.

2. A from the first parent with a from the second parent results in Aa.

3. a from the first parent with A from the second parent also results in Aa (not a new combination, just a repeat).

4. a from the first parent with a from the second parent results in aa.

Thus, the possible combinations of genotypes that can arise from two heterozygous parents (Aa x Aa) are AA, Aa, and aa. The distinct genotypes generated are therefore AA, Aa (considered as one genotype due to its occurrence twice), and