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Question: Answered & Verified by Expert
A woman with two genes (one on each X -chromosome) for haemophilia and one gene for colour blindness on the X-chromosome marries a normal man. How will the progeny be?
BiologyPrinciples of Inheritance and VariationJIPMERJIPMER 2011
Options:
  • A All sons and daughters are haemophilic and colourblind
  • B Haemophilic and colourblind daughters
  • C $50 \%$ haemophilic colourblind sons and $50 \%$ haemophilic sons
  • D $50 \%$ haemophilic daughters and $50 \%$ colourblind daughters
Solution:
1128 Upvotes Verified Answer
The correct answer is: $50 \%$ haemophilic colourblind sons and $50 \%$ haemophilic sons
Haemophilia and colour blindness both are recessive X-linked traits. They express in males when present in single copy (heterozygous) but in females, they express only when present in homozygous condition.

Results
(a) $50 \%$ sons are colourblind and haemophilic.
(b) $50 \%$ sons are haemophilic only.
(c) $50 \%$ daughters are carrier for colour blindness and haemophilia.
(d) $50 \%$ daughters are carrier for haemophilia only.

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