Question

in a group of snapdragons, some plants have red petals, some have white petals, and some have pink petals. petal color is dependent on anthocyanin production. in this group, one of the genes for anthocyanin production has two alleles. the allele for anthocyanin production that results in red petals (a^r) is incompletely dominant over the allele for no anthocyanin production that results in white petals (a^w). so heterozygotes have pink petals. complete the punnett square to show all possible genotypes of the offspring from a cross between two snapdragons: one with pink petals and one with white petals.

Explanation:

Step1: Determine the genotypes of the parents

The pink - petaled snapdragon has the genotype \(A^{R}A^{W}\) (heterozygous), and the white - petaled snapdragon has the genotype \(A^{W}A^{W}\) (homozygous recessive).

Step2: Set up the Punnett square

For a cross between \(A^{R}A^{W}\) (pink) and \(A^{W}A^{W}\) (white), the gametes of the pink - petaled parent are \(A^{R}\) and \(A^{W}\), and the gametes of the white - petaled parent are \(A^{W}\) and \(A^{W}\).
When we fill in the Punnett square:

• The first cell (from \(A^{R}\) of the pink parent and \(A^{W}\) of the white parent) has the genotype \(A^{R}A^{W}\)
• The second cell (from \(A^{R}\) of the pink parent and \(A^{W}\) of the white parent) has the genotype \(A^{R}A^{W}\)
• The third cell (from \(A^{W}\) of the pink parent and \(A^{W}\) of the white parent) has the genotype \(A^{W}A^{W}\)
• The fourth cell (from \(A^{W}\) of the pink parent and \(A^{W}\) of the white parent) has the genotype \(A^{W}A^{W}\)

Answer:

The genotypes of the offspring are \(A^{R}A^{W}\) (pink) and \(A^{W}A^{W}\) (white) in a 1:1 ratio. So the Punnett square cells (from left - to - right and top - to - bottom) should be filled as \(A^{R}A^{W}\), \(A^{R}A^{W}\), \(A^{W}A^{W}\), \(A^{W}A^{W}\)