Understanding Monohybrid Cross: Phenotypes of Dominant Alleles

Phenotype of Dominant Allele in Monohybrid Cross

In a monohybrid cross, is the phenotype of a dominant allele ever seen in the F1 progeny?

1) True

2) False

Final answer:

In a monohybrid cross, the phenotype of a dominant allele is always seen in the F1 progeny, as they inherit the dominant allele from one of the true-breeding parents. The correct option is 1) True

Explanation:

The phenotype of a dominant allele can indeed be seen in the F1 progeny during a monohybrid cross. A classic example involves the cross between true-breeding pea plants with dominant yellow seeds (YY) and recessive green seeds (yy). All the resulting F1 offspring will have a genotype of Yy, displaying the dominant yellow seed phenotype. This outcome is predicted using a Punnett square, which shows that each F1 offspring inherits the dominant yellow allele from one parent and the recessive green allele from the other, resulting in the yellow phenotype being expressed in every F1 individual.

When these heterozygous F1 individuals (Yy) are self-crossed or crossed amongst themselves, they produce F2 offspring with genotypes in a ratio of 1:2:1 (homozygous dominant: heterozygous: homozygous recessive) and a phenotypic ratio of 3:1 (dominant to recessive phenotypes). Therefore, the F1 progeny do display the phenotype of the dominant allele from their parents. The correct option is 1) True