When will wrinkled seeds appear in a cross between two hybrid round-seeded pea plants?

Correct answer: When offspring receive recessive factors from both sides

Let round seed be represented by R, the dominant allele, and wrinkled seed by r, the recessive allele. Two hybrid round-seeded plants have genotype Rr. In the cross Rr × Rr, the possible genotypes are RR, Rr, Rr, and rr. Only rr expresses the recessive wrinkled phenotype, so the seeds appear wrinkled when both parents contribute r; this is about one-fourth of the offspring.