Question

Dihybrid crosses

1. In man, assume that spotted skin (S) is dominant over non-spotted skin (S) and that wooly hair (W) is dominant over non-wooly hair (W). cross a marriage between a heterozygous spotted, non-wooly man with heterozygous wooly-haired, non-spotted woman. Give genotypic and phenotypic ratios of offspring?​

Answer 1

Step-by-step explanation:

The phenotypes and genotypes of the progeny can be determined by a dihybrid cross of the parents.

The heterozygous male will have the genotype 'SSww' and the heterozygous female will have the genotype 'ssWW'.

When crossed, the F1 offsprings will have a hybrid genotype of 'SsWw'. These offsprings are heterozygous with spotted skin and wooly hair.

On self-crossing of the F1 hybrids, we find four different combinations of the alleles- SW, Sw, SW and sw. The probability of getting each of these combinations is 1/4.

Hence, the probability of any dihybrid type is 1 out of the 16 possible genotypes. Using Punnet square, we find

9 SSWW: 3 SSww: 3 ssWW : 1 ssww

This is the phenotypic ratio of the offsprings.

The ratio of the possible genotypes will be 1:2:1:2:4:2:1:2:1.