Answer:
1) Aa refers to the heterozygous of the genes. In this gene, both allele are different from one another.
2) AA is a gene which is homozygous in nature. Homozygous means that both allele are the same. Capital letters i. e. AA is used for the trait that is dominant.
3) aa is a gene which is homozygous in nature. Lower case letters i. e. aa is refer for the trait that is recessive.
