Answer :
Final answer:
Without more data, a test cross of three offspring all with round peas does not conclusively indicate if the round pea plant is homozygous dominant or heterozygous. For a dihybrid cross of PpYY x ppYy, a 4x4 Punnett square is needed for analysis. The correct option is a) WW.
Explanation:
The correct representation of a dominant homozygous genotype for a pea plant with round peas is 'RR'. Since round peas (R) are dominant over wrinkled peas (r), a plant with a homozygous dominant genotype would possess two dominant alleles, hence RR. The given options in the question don't directly reflect the correct representation for a homozygous dominant genotype specific to round or wrinkled peas, but based on standard conventions for genotypic representation where dominant alleles are indicated by uppercase letters and recessive alleles by lowercase, the best fit would be option a. WW.
To determine if a plant with round peas is homozygous dominant (RR) or heterozygous (Rr), a test cross with a homozygous recessive (rr) would reveal the genotype of the unknown plant based on the offspring's phenotypes. If any of the offspring have wrinkled peas, the unknown genotype must be heterozygous. With only three offspring exhibiting round peas, statistical certainty is insufficient; a larger sample size is necessary for conclusive results.
A dihybrid cross involving two genes is shown in a Punnett square analysis of a pea plant cross between genotypes PpYY (purple flowers, yellow peas) and ppYy (white flowers, green peas). To complete this analysis, a Punnett square requires 16 squares (a 4x4 grid) since each parent can produce four different types of gametes (PY, Py, pY, py for the PpYY plant, and py, py, py, py for the ppYy plant).
