Question

Given below is a schematic representation of the inheritance of the shape of the seeds of garden peas. Answer the questions that follow:

1. Which is the dominant and recessive allele of the trait?
2. What does the ratio 3 : 1 in the F₂ generation represent?
3. State Mendel's Law of Dominance.

Answer 1

1. The dominant allele is R (for round seeds), while the recessive allele is r (for wrinkled seeds). This is obvious because only round seeds develop in F₁, whereas the wrinkled characteristic is entirely concealed.
2. 3:1 indicates that three of the four seeds are spherical and one is wrinkled. That is, 75% of the F₂ progeny have round seeds (the dominant characteristic), but only 25% have wrinkled seeds (the recessive trait).
3. Mendel's law of dominance states that if an organism has two distinct alleles for a trait, the dominant allele will be expressed, hiding the recessive allele. This means that only the dominant allele determines the organism's phenotype.