What is the ratio of offspring phenotypes if the dominant phenotype is green and the recessive phenotype is yellow?

In a typical Mendelian inheritance scenario involving a single trait, when one parent is homozygous dominant (GG) for the dominant phenotype (green) and the other parent is homozygous recessive (yy) for the recessive phenotype (yellow), the resulting offspring from this cross would all exhibit the dominant phenotype since they inherit one dominant allele from the green parent and one recessive allele from the yellow parent (Gg).

When a Gg offspring then self-fertilizes or is crossed with another Gg, the potential combinations of alleles can be arranged in a Punnett Square. This results in three combinations that display the dominant phenotypes (GG and Gg) and one combination that displays the recessive phenotype (yy). Therefore, the offspring phenotypic ratio here would be three green (dominant) to one yellow (recessive), leading to a 3:1 ratio.

This ratio is characteristic of a monohybrid cross where both parents are heterozygous for the trait considered, confirming that the correct answer is indeed 3:1. The other ratios listed (2:1, 1:2:1, and 4:1) would apply under different genetic circumstances or traits, but