Final answer:
To find the phenotypic and genotypic ratios of pea plants heterozygous for seed shape and color (SsYy x SsYy), the FOIL method is used to determine gametes, followed by creating a 16-square Punnett square. The typical genotypic ratio for this dihybrid cross is 9:3:3:1, and the phenotypic ratio follows with 9 round yellow, 3 round green, 3 wrinkled yellow, and 1 wrinkled green offspring.
Step-by-step explanation:
To determine the phenotypic and genotypic ratios of the offspring of pea plants that are heterozygous for both seed shape and color (SsYy x SsYy), we can apply the Punnett square method. We first use FOIL (First, Outer, Inner, and Last) to determine the different types of gametes that can be produced by a heterozygous pea plant. For the genotype SsYy, the gametes could be SY, Sy, sY, and sy.
When these gametes combine during fertilization, the resulting genotypes can be set out in a 16-square Punnett square. The genotypic ratio for this dihybrid cross typically comes out to 9:3:3:1, which represents the number of offspring with the following genotypes: S_ Y_ (round, yellow), S_ yy (round, green), ss Y_ (wrinkled, yellow), and ss yy (wrinkled, green). The phenotypic ratio also follows the combination of traits, resulting in 9 round yellow, 3 round green, 3 wrinkled yellow, and 1 wrinkled green.
It is important to note that the genotype S_ denotes having at least one dominant allele S (homozygous SS or heterozygous Ss), and Y_ represents having at least one dominant allele Y (homozygous YY or heterozygous Yy). The ratio reflects the principle of independent assortment, which states that alleles for different traits are distributed to sex cells (gametes) independently of one another.