The partial Punnett square shows a cross between two pea plants with genotypes RR and Rr. The allele for round seeds (R) is dominant, and the allele for wrinkled seeds (1) is recessive R R. R What fraction of the offspring of this cross are expected to have round seeds?
The shape and color traits of the pea plant follow the mendelian law of independent assortment. The genes are located on different loci of the chromosomes and do not affect each other. The punnett square for the heterogenous traits of both color and shape will have the two shape alleles (Rr) assorting with the two color alleles (Yy). The gametes in the cross will be RY, Ry, rY and ry. The gametes from the two plants will cross over to result in the formation of a combination of 4 different phenotypes in the ratio of 9:3:3:1 (image). Thus from this ratio we can predict that if the crosses are between plants heterozygous for color and shape trait, then 9 will be round and yellow colored seeds.
