Biology Inheritance / Variation & Genetics SZABMU 2024
PMDC Verified Question 13 of 94
Hemophilia A and B pass from infected ____ grandfather to ____ through carrier daughter.
A
Paternal, grandson
B
Maternal, grandson
C
Paternal, granddaughter
D
Maternal, granddaughter
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Maternal, grandson
Concept:

X-linked recessive traits characteristically exhibit a "zig-zag" pattern of inheritance across generations.

Solution:

  • An affected male (\(X^h Y\)) will pass his mutated X chromosome to his daughter, making her a carrier (\(X^H X^h\)). He does not pass it to his sons.
  • This carrier daughter can then pass the mutated \(X^h\) chromosome down to her sons (who will express the disease) or daughters (who will be carriers).
  • Therefore, the disease visibly skips a generation, moving from a maternal grandfather to his grandson via his carrier daughter.


Why other options are incorrect:

  • It cannot pass paternally (father to son) because a father only gives a Y chromosome to his son, and the hemophilia gene is on the X chromosome.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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