Question

In maize (corn) plants, a dominant allele I inhibits kernel color, while the recessive allele i permits color when homozygous. At a different locus, the dominant allele P causes purple kernel color, while the homozygous recessive genotype pp causes red kernels. If plants heterozygous at both loci are crossed, what will be the genotypic and phenotypic ratios of the offspring?

Answer 1

Answer:

Phenotype ratio= 12 colorless : 3 purple : 1 red

Genotype ratio= 1:2:1:2:4:2:1:2:1

Explanation:

According to the given information, the dominant allele "I" is epistatic to P and p alleles and presence of "I" inhibits the expression of both "P" and "p" alleles.

A cross between two heterozygous plants for both locus would give the F2 progeny in 12 colorless: 3 purple: 1 red ratio.

Here, the F2 genotype with "I-G" and "I-gg" would produce colorless kernels while the ones with "ii-G-" would exhibit purple colored kernels. The F2 genotype "iigg" would beak red kernels.

Hence, the phenotype ratio= 12 colorless : 3 purple : 1 red

Genotype ratio would be same as for the mendelian dihybrid cross= 1 IIPP: 2 IIPp :1 IIpp: 2 IiPP :4 IiPp: 2 Iipp: 1 iiPP :2 iiPp: 1 iipp