How to Determine Dominance in a Monohybrid Cross

What phenotypic ratios suggest dominance in a monohybrid cross?

Final answer:

A 3:1 phenotypic ratio suggests dominance in a monohybrid cross. In the resulting offspring, three-quarters would display the dominant trait and a quarter would exhibit the recessive trait. This follows the rules of Mendellian genetics regarding independent assortment and dominance.

When trying to determine dominance in a monohybrid cross, one key indicator is the phenotypic ratio among the progeny. A 3:1 phenotypic ratio suggests that the dominant trait is at play. In this scenario, three-quarters of the offspring would display the dominant trait, while a quarter would exhibit the recessive trait.

This ratio follows the principles of Mendellian genetics, specifically the concepts of independent assortment and dominance. Through independent assortment, alleles for different traits segregate independently into gametes, resulting in various combinations. Meanwhile, dominance dictates which allele is expressed in the phenotype when an individual carries different alleles for a specific trait.

For instance, in a monohybrid cross involving pea plants with smooth (dominant) and wrinkled (recessive) textures, a 3:1 phenotypic ratio would mean that three-quarters of the offspring show a smooth texture (dominant trait), while a quarter exhibit a wrinkled texture (recessive trait).