How many combinations of alleles could there be in zygotes produced by crossing the following parents TT x Tt?

When crossing the parents TT (homozygous dominant) and Tt (heterozygous), the possible combinations of alleles in the zygotes can be determined. The TT parent can only contribute a T allele, while the Tt parent can contribute either a T or a t allele. Therefore, the possible combinations of alleles in the zygotes are TT and Tt, resulting in two distinct combinations.