Question

A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was 6 feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. ____ 15) How many of the couple's daughters might be expected to be color-blind dwarfs? A) all B) one out of four C) half D) none E) three out of four

Answer 1

Answer:

Half of the males are colorblind, dwarf and the other half colorblind, normal height.

Explanation:

The achondroplastic dwarf man with normal vision has a DdXY genotype. He marries a color-blind woman of normal height, so the hergenotype is ddX (c) X (c). All males will be colorblind as they inherit the X (c) chromosome from their mother. Half of them will be of normal height. So half of her boys will be colorblind and of normal height. To see how it works genetically, the cross is:

DdXY x ddX (c) X (c)

Your children have one of the four possible genotypes:

DdXX (c) (female, normal vision, colorblind carrier, dwarf)

DdX (c) Y (male, colorblind, dwarf)

ddXX (c) (woman, normal vision, color blindness carrier, normal height)

ddX (c) Y (male, colorblind, normal height)