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NEET 2005
Exam
NEET
Year
2005
Subject
Zoology
Chapter
Principles of Inheritance and Variation

NEET 2005 · Zoology · Principles of Inheritance and Variation

Haemophilia is more commonly seen in human males than in human...

Haemophilia is more commonly seen in human males than in human females because:

Options

  1. Aa greater proportion of girls die in infancy
  2. Bthis disease is due to a Y-linked recessive mutation
  3. Cthis disease is due to an X-linked recessive mutation
  4. Dthis disease is due to an X-linked dominant mutation.

Correct answer

C. this disease is due to an X-linked recessive mutation

Step-by-step solution

Haemophilia being a sex chromosome related recessive disorder has its gene present on X\mathrm{X} chromosome. Since males have one X\mathrm{X} and one Y\mathrm{Y} chromosome, and the genes present on X\mathrm{X} don't have counter genes on Y\mathrm{Y}, only one affected gene (to be present on X\mathrm{X} ) is required for the disease in males. While in females, there are 2X2 \mathrm{X} chromosomes. For the disease to occur both the X\mathrm{X} chromosomes should have the affected genes which is a rare chance. For this to be possible, the father of the female must be diseased while the mother must atleast be a carrier.
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