In a cross between RRYY (round yellow seeds of pea plant) and rryy (green wrinkled seeds of pea plant), Mendel found that all F1 offspring would be RrYy i.e. Round yellow. Hence Mendel was able to deduce that round is dominant over wrinkled whereas yellow is dominant over green.
The F1 dihybrid plants produced four types of gametes i.e. YR, Yr, yR and yr. When crossed, they would give the following possible offspring:
9 round-yellow : 3 wrinkled-yellow : 3 round-green : 1 wrinkled-green pea seeds.