Question

Gray seed color in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white.
(a) What is the most probable genotype of each parent?

(b) Based on your answer in (a) above, what genotypic and phenotypic ratios are expected in these progeny? (Assume the following symbols: G = gray and g = white.)
A) (a) GG . gg; (b) genotypic = 3:1, phenotypic = 1:2:1
B) (a) Gg . Gg; (b) genotypic = 1:2:1, phenotypic = 3:1
C) (a) GG . Gg; (b) genotypic = 1:2:1, phenotypic = 2:1
D) (a) gg . Gg; (b) genotypic = 1:2, phenotypic = 3:1

Answer 1

Answer:

(a) Gg × Gg; (b) genotypic = 1:2:1, phenotypic = 3:1

Explanation:

a) A cross between two gray seeded plants produces progeny with gray and white seeds in 3:1 ratio (302:98=3:1). This means that the parent plants are heterozygous and each has at least one recessive allele. If the allele "G" is responsible for gray seed and the allele "g" imparts white color to the seeds, the genotype of the heterozygous parents would be "Gg".  

b) A cross between two heterozygous gray seeded parents would produce progeny in following ratio:

Genotype ratio= 1 GG: 2 Gg: 1 gg

Phenotype ratio= 3 Gray: 1 white