Question

A man who has hemophilia (X linked recessive) marries a woman who is a carrier. What percentage of the offspring have the disease?

Answer 1

Answer:

50% of the progeny will be hemophilic

Explanation:

Available data:

• Hemophilia is an X linked recessive affection
• Let us say that the gene for hemophilia is H
• + is the dominant allele ----> X⁺ Normal
• - is the recessive allele  ----> X⁻ Hemophilic

Cross: A man who has hemophilia with a woman who is a carrier

Parentals)  X⁻ Y      x      X⁺X⁻

Gametes) X⁻     Y         X⁺     X⁻

Punnett square)   X⁻          Y

                 X⁺     X⁺X⁻        X⁺Y

                 X⁻     X⁻X⁻        X⁻Y

F1)  

• 2/4 = 1/2 = 50% pf the progeny will be boys
• 2/4 = 1/2 = 50% of the progeny will be girls

• 2/4 = 1/2 = 50% pf the progeny will be healthy
• 2/4 = 1/2 = 50% of the progeny will be hemophilic

• 1/4 = 25% of the progeny will be healthy carriers girls, X⁺X⁻
• 1/4 = 25% of the progeny will be healthy boys, X⁺Y
• 1/4 = 25% of the progeny will be hemophilic girls, X⁻X⁻
• 1/4 = 25% of the progeny will be hemophilic boys, X⁻Y