Question

1. gray seed coat color is dominant over green seed coat color in pea plants. fill in the punnett square and determine the expected genotypic and phenotypic ratios from crossing homozygous dominant and homozygous dominant parents. genotypes: __________ genotypic ratio: ____ phenotypes: ________ phenotypic ratio: ______

Explanation:

Step 1: Determine Parent Genotypes

Let the dominant allele for gray seed coat be \( G \) and the recessive allele for green seed coat be \( g \). Both parents are homozygous dominant, so their genotypes are \( GG \). Each parent will produce gametes that are all \( G \) (since homozygous dominant individuals have only \( G \) alleles to pass on).

Step 2: Fill in the Punnett Square

When we cross two \( GG \) parents, we put the gametes from one parent along the top of the Punnett square and the gametes from the other parent along the side. Since both parents produce only \( G \) gametes, each cell in the Punnett square (which represents the possible genotype of the offspring) will have the genotype \( GG \).

Step 3: Determine Genotypes and Genotypic Ratio

All of the offspring have the genotype \( GG \). So the only genotype present is \( GG \). If we consider the ratio of \( GG \) to other possible genotypes (but there are no other genotypes here), the genotypic ratio is \( GG: \text{non - }GG=4:0 = 1:0 \) (or we can say all offspring are \( GG \), so the ratio is \( 1 \) (for \( GG \)) with no other genotypes).

Step 4: Determine Phenotypes and Phenotypic Ratio

The dominant allele \( G \) codes for gray seed coat. Since all offspring have the \( GG \) genotype (homozygous dominant), they will all express the gray seed coat phenotype. The phenotypic ratio of gray to green seed coat is \( 4:0 = 1:0 \) (or all gray, so the ratio is \( 1 \) for gray with no green).

Answer:

Punnett Square:

	G	G
G	GG	GG

Genotypes: \( GG \) (all offspring)

Genotypic Ratio: \( 1:0 \) (or simply all \( GG \), so ratio of \( GG \) to any other genotype is \( 4:0 \) which simplifies to \( 1:0 \) if considering non - existent genotypes, but more accurately, since all are \( GG \), the ratio is \( GG: \text{other} = 4:0 = 1:0 \))

Phenotypes: Gray seed coat (all offspring)

Phenotypic Ratio: \( 1:0 \) (or \( 4:0 \) which simplifies to \( 1:0 \) for gray to green, since all are gray)