Question

With reference to flower colour two independent crosses were made, one between true breeding garden pea plants and another between true breeding Antirrhinum plants. Write the phenotypes of their F₁-progeny. Justify your answer giving reason.

Answer 1

When true-breed pea plants with purple flowers (PP) are mixed with true-breed pea plants with white flowers (pp), the offspring have all purple flowers (Pp). This is because the weak allele (p) for white colour hides the strong allele (P) for purple colour.

Crossing true-breed Antirrhinum plants with red flowers (RR) with true-breed Antirrhinum plants with white flowers (rr) make F1 plants with all pink flowers (Rr). Because of partial dominance, the heterozygous condition (Rr) creates a phenotype that is in the middle of the two homozygous conditions (red and white). This phenotype is pink.

Therefore, the phenotypes of the F₁ progeny would be:

• For garden pea plants: All plants with purple flowers.
• For Antirrhinum plants: All plants with pink flowers.