Question

Which disease will show the following mode of inheritance?

• A. Wiskott (Wiskott-Aldrich syndrome)
• B. Wilson
• C. Prader willi
• D. Achondroplasia

Hint:

Only males affected, passed by carrier females, no father-to-son transmission = X-linked recessive — which listed disease is X-linked?

Answer 1

The Correct Option is A

Step 1: Interpret the pedigree. The chart is a family pedigree (squares = males, circles = females; filled = affected). The pattern shown - only males affected, transmission through unaffected (carrier) females, no male-to-male transmission, and carrier females marked with a central dot - is the classic picture of X-linked recessive inheritance.

Step 2: Match the inheritance to a listed disease. Among the four options, the only X-linked recessive condition is Wiskott-Aldrich syndrome (immunodeficiency with eczema and thrombocytopenia, due to a mutation in the WAS gene on the X chromosome). Therefore Option A fits the pedigree.

Step 3: Select the answer. X-linked recessive pedigree → Wiskott-Aldrich - Option A (consistent with the printed key, Ans. A).

Step 4: Why the others are wrong. (B) Wilson disease is autosomal recessive (ATP7B) - affects both sexes equally with horizontal pattern, not X-linked. (C) Prader-Willi syndrome results from loss of the paternal 15q11-13 region (imprinting/microdeletion), not an X-linked recessive pedigree. (D) Achondroplasia is autosomal dominant (FGFR3) - vertical transmission affecting both sexes, including male-to-male, which is absent here.

Final Answer: Option A - Wiskott-Aldrich syndrome.