Question

Match the genetic disorders in Column I to the corresponding underlying cause in Column II.

Column I	Column II
P. Klinefelter Syndrome	1. X-chromosome insufficiency
Q. Turner syndrome	2. DNA helicase mutations
R. Bloom syndrome	3. Nucleotide excision repair defects
S. Xeroderma pigmentosum	4. Extra X chromosome(s) in a male

• A. P-1; Q-3; R-4; S-2
• B. P-4; Q-1; R-2; S-3
• C. P-4; Q-2; R-3; S-1
• D. P-3; Q-2; R-4; S-1

Hint:

Klinefelter is an extra X in a male, Turner is a single X, Bloom is a helicase defect, and Xeroderma pigmentosum is a repair defect; check this against the given options.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Each disorder in Column I has one specific, well documented molecular or chromosomal cause in Column II. We match each one from known genetics facts rather than by elimination.

Step 2: Key Formula or Approach:
Sex chromosome disorders (Klinefelter, Turner) are matched to the two chromosome-count descriptions (extra X in a male, X insufficiency), and the two DNA repair disorders (Bloom, Xeroderma pigmentosum) are matched to the two DNA repair/helicase descriptions.

Step 3: Detailed Explanation:
Klinefelter syndrome karyotype is 47,XXY: an extra X chromosome in a male, so P-4.
Turner syndrome karyotype is 45,X: only one X chromosome is present, a clear X-chromosome insufficiency, so Q-1.
Bloom syndrome is caused by loss of function of the BLM helicase gene, a RecQ-family DNA helicase, so R-2 (DNA helicase mutations).
Xeroderma pigmentosum is caused by defects in the nucleotide excision repair pathway (the XPA to XPG genes), so S-3 (nucleotide excision repair defects).
This gives the full match P-4; Q-1; R-2; S-3, which is option (B).

Step 4: Final Answer:
Based on standard genetics facts, the correct match is P-4; Q-1; R-2; S-3 (option B). This matches the official answer, option (B).