Question

State Mendel’s law of dominance. How did he deduce the law? Explain with the help of a suitable example.

Answer 1

This law states that traits are controlled by distinct units called factors (genes), which occur in pairs. In a monohybrid cross, the dominant allele expresses itself and masks the effect of the recessive allele. However, the recessive allele is not lost; it remains hidden in the F₁ generation and appears again in the next generation. According to this law, only one of the parental traits is expressed in the F₁ generation, while both traits appear in the F₂ generation. For example, when pea plants with round seeds (RR) are crossed with plants having wrinkled seeds (rr), all the seeds in the F₁ generation are round (Rr). When these F₁ plants are self-pollinated, both round and wrinkled seeds appear in the F₂ generation in a 3 : 1 ratio. Thus, the dominant trait (round seeds) is expressed in F₁, while the recessive trait (wrinkled seeds), though suppressed earlier, reappears in F₂.