Exemplar Problems

Question:

Explain the Law of Dominance using a monohybrid cross.

Answer:

The Law of Dominance states that in a heterozygous individual with two different alleles for a specific trait, one allele (dominant) will determine the phenotype, while the other allele (recessive) will have no observable effect on the phenotype.

In a monohybrid cross, consider a cross between a homozygous dominant (AA) individual and a homozygous recessive (aa) individual for a specific trait. The offspring (F1 generation) will all have the dominant phenotype (expressing the dominant allele). Only in the F2 generation, when these F1 individuals are allowed to self-cross, will the recessive phenotype reappear in a 3:1 ratio, demonstrating the Law of Dominance.