Answer:
25% or 1/4
Explanation:
This is a monohybrid cross involving pea color gene. The yellow allele (Y) is dominant over green allele (y). According to the question, a pure line yellow pea plant (YY) is crossed with a pure line green pea plant (yy) to produce a hybrid F1 offspring (Yy).
N.B: A pure line is a plant that has identical alleles for a specific trait (pea color in this case).
The F1 offsprings were self-crossed (see attached image) to produce four possible F2 offsprings; YY, Yy, Yy, yy
Among these four F2 offsprings, YY and yy are purelines or homozygous because they contain same alleles while Yy's are hybrids. The question says purebreeding plant that produces only yellow peas i.e. an homozygous dominant pea plant (YY). yy is an homozygous (purebreeding) green pea plant.
Therefore, the proportion of purebreeding plants that produces yellow peas in the F2 generation is 1/4 or 25%.
