Use the words 'homozygous', 'heterozygous, dominant
and 'recessive' (where suitable) to describe the following allele combinations: Aa, AA, aa.

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.

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.