Final answer:
The F1 generation resulting from a cross between a heterozygous yellow pea plant (Yy) and a homozygous recessive green pea plant (yy) would have a phenotypic ratio of 1 yellow to 1 green (50% yellow and 50% green seeds).
Step-by-step explanation:
In a Mendelian experiment on pea seed color, crossing a heterozygous yellow seed-bearing plant (Yy) with a homozygous recessive green seed-bearing plant (yy) results in F1 offspring with a phenotypic ratio of 1 yellow to 1 green. This is because the heterozygous (Yy) parent can only pass on either a Y (yellow) or y (green) allele, and the green (yy) parent can only pass on a y allele. So, the possible combinations for the offspring are Yy (yellow) and yy (green). A Punnett square analysis can be used to determine that half of the offspring will be Yy and half will be yy. Since yellow (Y) is dominant over green (y), the visible phenotype will be 50% yellow and 50% green seeds, or simply a 1:1 ratio. Mendel's experiments further showed that when these F2 heterozygous yellow plants (Yy) are self-crossed, a 3:1 phenotypic ratio of yellow to green will be observed in the F3 generation.