Question

An achondroplastic male dwarf with 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. 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?
a.all
b.one out of four
c.none
d.three out of four
e.half

Answer 1

No daughters of the achondroplastic male dwarf and color-blind woman would be expected to be color-blind dwarfs. All daughters will inherit dwarfism due to the autosomal dominant nature of achondroplastic dwarfism, but they will only be carriers of color blindness, not affected by it, because of the X-linked recessive inheritance pattern.

Step-by-step explanation:

The question asked is about the inheritance of achondroplastic dwarfism and red-green color blindness, which are two genetically inherited conditions. Achondroplastic dwarfism is an autosomal dominant condition, meaning that if one copy of the mutant gene is present, the individual will display the trait. Red-green color blindness is an X-linked recessive disorder, which means males are more frequently affected because they only have one X chromosome, and females are usually carriers unless they inherit two copies of the allele for the condition.

Given that the father is an achondroplastic male with normal vision (let's symbolize the achondroplasia gene as 'A' and its normal allele as 'a') and the mother is a color-blind woman of normal height (Let's symbolize the color blindness gene as 'Xc' and the normal color vision allele as 'Xn'), their daughters could inherit either 'A' or 'a' from their father and either 'Xc' or 'Xn' from their mother.

Since the father has one dominant 'A' allele, all daughters will inherit this allele, making all daughters dwarfs. However, daughters will inherit one X chromosome from their mother, who is color-blind (XcXc). Since the father has normal color vision, he provides an X chromosome with a normal vision allele (Xn), making the daughters carriers of the color-blind gene but not color-blind themselves. Therefore, none of their daughters would be expected to be color-blind dwarfs.

In summary, even though all daughters will inherit dwarfism due to the dominance of the achondroplastic gene, they will not express the color-blind trait due to receiving a normal color vision allele from their father. Thus, the correct answer to this question is c. none.