You want to determine the pea color genotype of a pea plant with yellow peas. You conduct a test cross with your mystery pea plant. The test cross results in 50% of the offspring possessing yellow peas and 50% of the offspring possessing green peas. What is the genotype for pea color of the mystery parent?

• A. YY.
• B. Yy.
• C. yy.
• D. None of the above.

Answer: (B)

Verified step by step guidance

1. Understand the concept of a test cross: A test cross involves breeding an individual with a dominant phenotype (but unknown genotype) with an individual that is homozygous recessive for the trait in question. This helps to determine the genotype of the dominant phenotype individual.
2. Identify the phenotypes and genotypes involved: Yellow peas are dominant (Y) and green peas are recessive (y). The mystery pea plant has yellow peas, so its genotype could be either homozygous dominant (YY) or heterozygous (Yy).
3. Analyze the test cross results: The offspring show a 50% yellow and 50% green pea phenotype. This indicates that the mystery pea plant must have contributed both a dominant allele (Y) and a recessive allele (y) to the offspring.
4. Determine the genotype of the mystery parent: Since the offspring are 50% yellow and 50% green, the mystery parent must be heterozygous (Yy). This is because a homozygous dominant (YY) parent would produce 100% yellow offspring when crossed with a homozygous recessive (yy) parent.
5. Conclude the genotype: Based on the test cross results, the genotype of the mystery pea plant is Yy, which explains the 50% yellow and 50% green offspring.