Given below is a schematic representation of the inheritance of the shape of seeds of garden pea. Answer the questions that follow.
Which is the dominant and recessive allele of the trait?
Topic: Dominant and recessive alleles
Answer
ROUND seed shape is the DOMINANT allele (R). WRINKLED seed shape is the RECESSIVE allele (r).
HOW YOU CAN TELL FROM THE DIAGRAM without being told: in a monohybrid cross between two pure parents, the character that appears in ALL the F1 offspring is the DOMINANT one; the character that DISAPPEARS in F1 and REAPPEARS in F2 is RECESSIVE.
Round appears throughout F1, so round is dominant. Wrinkled vanishes in F1 and returns in a quarter of F2, so wrinkled is recessive.
That reappearance is the crucial observation Mendel made: the recessive character was never lost, only MASKED, and it must therefore have been carried unchanged through the F1 generation. It is the whole basis of the idea of a gene as a discrete particle.