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 a heterozygous wooly-haired, non-spotted woman. Give genotypic and phenotypic ratios of offspring.

The branch of science which deals with the gene and inheritance is called genetics.

The correct answer is 1:2:1 and 3:1

The cross between two characters is called a dihybrid cross.

According to the question, the parent's genes are Ss and Ww.

The gamete formed during the gametogenesis is S and s for one parent and W and w for another.

This gamete and fused with any of the gametes to increase the variation.

After the cross the result is

SW, Sw, sW, and sw.

Hence the genotype ratio is 1:1:1:1 but the phenotype ratio is spotted skin: nonspotted skin is 2:2.

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Total four genotypes and its frequency  

SsWw – 4/16

ssWw- 4/16

Ssww - 4/16

ssww - 4/16

Phenotype –  

SsWw – Heterozygous  Spotted skin and heterozygous wooled hair

ssWw  - Homozygous non-spotted skin and heterozygous wooled hair

Ssww  -  Heterozygous  Spotted skin and Homozygous non -wooled hair

ssww  - Homozygous non-spotted skin  and Homozygous non -wooled hair

Explanation:

Given -

Allele for spotted skin is "S"

Allele for non-spotted skin is "s"

Allele for Wooly hair is "W"

Allele for non-wooly hair is "w"

Allele "S" is dominant over "s"

And Allele "W" is dominant over "w"

Cross is carried out between heterozygous spotted, non-wooly man and heterozygous wooly-haired, non-spotted woman

Genotype of heterozygous spotted, non-wooly man - Ssww

Genotype of  heterozygous wooly-haired, non-spotted woman - ssWw

Ssww * ssWw

Sw         Sw         sw         sw

sWSsWwSsWwssWwssWw

swSswwSswwsswwssww

sWSsWwSsWwssWwssWw

swSswwSswwsswwssww

Total four genotypes and its frequency  

SsWw – 4/16

ssWw- 4/16

Ssww - 4/16

ssww - 4/16

Phenotype –  

SsWw – Heterozygous  Spotted skin and heterozygous wooled hair

ssWw  - Homozygous non-spotted skin and heterozygous wooled hair

Ssww  -  Heterozygous  Spotted skin and Homozygous non -wooled hair

ssww  - Homozygous non-spotted skin  and Homozygous non -wooled hair