Question

Refer to the following information to answer the questions below. 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. How many of their daughters might be expected to be color-blind dwarfs

Answer 1

None

Step-by-step explanation:

Given,

achondroplastic dwarfism = autosomal dominant trait

red-green colour blindness = X-linked recessive

Man : Given that he is dwarf but his father had normal height. Since this dwarfism is a dominant trait, his father must have aa combination to produce normal height. He received one "a" allele from his father but he is still dwarf which means that the second allele was dominant allele. Hence his genotype is Aa. He has normal vision which can be represented by XCY hence his total genotype is AaXCY.

Woman : Woman has normal height so her genotype must be aa. She is colourblind and in females two recessive alleles need to be present to produce the X linked recessive phenotype. Hence her total genotype would be aaXcXc.

When AaXCY X aaXcXc :

If we check individual crosses,

XC Y

Xc XCXc XcY

Xc XCXc XcY

All the daughters have XCXc genotype so they all will be carriers for colourblindness and none of them will be colour blind. Hence probability of having a colour blind dwarf daughter will be zero.