Question

A man who is a dwarf with achondroplasia and normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind with achondroplasia?

Answer 1

Answer:

None

Explanation:

Assuming the allele for height is T. Since dwarfism is autosomal dominant, a normal height person will be tt while a dwarf person will either be TT or Tt.

Hence, a man who is dwarf but has a normal height father will have a genotype of Tt and an average height woman will have a genotype of tt.

Tt   x   tt = 2Tt (dwarf), 2tt (normal height)

If the allele for vision is represented by B. A normal vision man will have the genotype $X^BY$ while a colour blind woman will have the genotype $X^bX^b$.

$X^BY$   x    $X^bX^b$  =  $X^BX^b, X^BX^b, X^bY, X^bY$

Since, colour blindness is X-linked and recessive, females need two alleles ( $X^bX^b$) in order to be affected and none of their daughters posses two alleles.

Hence, none of their daughters is expected to be colour blind with achondroplasia.