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ZoologyNEET 2025Sex determination, mutation, genetic disorders

Principles of Inheritance and Variation

With the help of the given pedigree, find out the probability for the birth of a child having no disease and being a carrier (has the disease mutation in one allele of the gene) in the F₃ generation.

Question 152 as printed in the NEET 2025 booklet

  1. A.1/4✓
  2. B.1/2
  3. C.1/8
  4. D.Zero

Solution

The pedigree fits X-linked recessive inheritance (affected F₀ mother → all daughters carriers; carrier mother → affected son). The F₂ cross is carrier female XAXaX^AX^a × affected male XaYX^aY: offspring XAXaX^AX^a (carrier daughter), XaXaX^aX^a (affected daughter), XAYX^AY (normal son), XaYX^aY (affected son), each 1/4. Probability of a disease-free carrier is 1/4.

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