Final answer:
A pea plant with a genotype of Yy is heterozygous with one dominant allele for yellow pea color, and its phenotype is yellow peas since the dominant allele masks the recessive one.
Step-by-step explanation:
If a pea plant is Yy, its genotype is heterozygous, meaning it has one dominant allele (Y) and one recessive allele (y). In this case, Y is the allele for yellow pea color, which is dominant, and y is for green pea color, which is recessive. Since the dominant allele masks the effect of the recessive allele in a heterozygote, the phenotype of this pea plant would be yellow peas.