A man who is an acho ndroplastic 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. Acho ndroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. What proportion of their sons would be color-blind and of normal height?

Half.

Explanation:

Autosominal dominant trait are express are able to express themselves in the homozygous dominant as well as in the heterozygous condition. The X-linked recessive traits are mostly expressed in males since they have only one X chromosome. Female shows X linked recessive trait when her both X chromosome are affected.

The achandroplastic dwarf man with normal vision is married with a color blind woman with normal height. The mother is affected with vision, she definitely pass this trait to his son. The male is affected with acho ndroplastic (may be homozygous dominant or heterozygous) and the female is normal (homozygous recessive). The probability can be calculated including both the achandroplastic and vision trait. Half of the males are color blind with normal height (multiplying the probability of vision and achandroplatic trait).