Since all of the offspring are tall with yellow seeds, tall and yellow are dominant. This suggests the the genotype of the tall and yellow plant is TTYY, and the genotype for the short and green plant is ttyy. In a cross between the two plants, each parent gives one allele for each gene. Since each parent only has one type of allele, all of the offspring are heterozygous for both traits, or TtYy.
