Suppose you have monohybrid pea plants in your garden and find that they produce round seed to wrinkled seeds in the ratio of 3:1. If the allele are designated (R & r) respectively, what is the probable Phenotype of the parents?

According to the question, a monohybrid cross involving a single gene coding for seed shape in pea plants is the case here. The allele for round seeds is R while allele for wrinkled seeds is r. The "R" allele is dominant over the "r" allele i.e. the phenotypic expression of r will be masked by R in a heterozygous state.

In order to get a ratio 3:1 of round seeds to wrinkled seeds offsprings, the parents will probably both have an Rr genotype, which is phenotypically round-seeded considering that round seeds (R) is dominant over wrinked seeds (r).

As seen in the punnet square attached as an image, four possible offsprings will be produced from a cross between parents Rr × Rr. The possible offsprings will have genotypes: RR, Rr, Rr, and rr.

RR, Rr, Rr are phenotypically round-seeded (3)

rr is phenotypically wrinkled-seeded (1).

Hence, the ratio 3 round seeds : 1 wrinkled seeds will be probably produced by parents with round seeds (Rr).