When a haemophilic carrier woman marries a normal man, who among her offspring may be affected?
Correct answer: C. Half of her sons
- A. All her children
- B. All her daughters
- C. Half of her sons
- D. None of these options
Explanation
Haemophilic female = XH Xh Normal male= XH Y Referring to the Punnett square, Half of daughters are affected as a carrier of haemophilia, while half males will be haemophilic (as they inherited the X chromosome from their mother who is a carrier).
This question appeared on the HEC Phase I 2017 paper, which you can sit online with every answer explained.
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About X-linked Recessive Inheritance
X-linked recessive inheritance involves genes on the X chromosome, so males express a recessive allele with no corresponding allele on their single X chromosome, while females may be carriers. Pedigrees cover haemophilia and red-green colour blindness, including carrier mothers, affected sons and the absence of father-to-son transmission.
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