The ratio of homozygous dominant and homozygous recessive in dihybrid cross for both characters will be
Mendel chose to cross a pea plant that was homozygous and dominant for round (RR), yellow (YY) seeds with a pea plant that was homozygous and recessive for wrinkled (rr), green (yy) seeds, represented by the following notation:
RRYY X rryy
Organisms in this initial cross are called the parental generation. The offspring of the RRYY X rryy cross, which is called the F1 generation, were all heterozygous plants with round, yellow seeds and the genotype RrYy. Next, Mendel crossed two plants from the F1 generation. This step is the dihybrid cross, and it is represented as:
RrYy x RrYy
Mendel observed that the F2 progeny of his dihybrid cross had a 9:3:3:1 ratio and produced nine plants with round, yellow seeds, three plants with round, green seeds, three plants with wrinkled, green seeds. From his experiment, Mendel observed that the pairs of traits in the parental generation sorted independently from one another, from one generation to the next.