Incontinentia pigmenti is a rare Xlinked dominant disorder i

Incontinentia pigmenti is a rare, X-linked dominant disorder in humans characterized by swirls of pigment in the skin. If an affected female, who had an unaffected father, has children with an unaffected male, what would be the predicted ratios of affected and unaffected sons and daughters?

Solution

Affected female with genotype X^pX had an unaffected father with genotype XY. So she inherited X^p from her mother with genotype X^pX

X^p - swirls of pigment in the skin

Unaffected male : XY

X^pX x XY

Possible genotypes

Affected daughter : X^pX

Affected son : X^pY

Unaffected daughter : XX

Unaffected son : XY

Ratio is 1:1:1:1