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Eduncle posted an MCQ
October 20, 2019 • 19:45 pm 0 points
  • CSIR NET
  • Life Sciences

In the following pedigree, individuals with shaded circle or shaded square show presence of a recessive autosomal trait.

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    Eduncle Best Answer

    The trait given is autosomal recessive. In this pedigree the man’s (II-3) parents must have both been heterozygotes Aa because they produced affected aa child. So among expected progeny of man’s (II-3) parents (AA(1/4) Aa(1/2)aa(1/4) : 2/3 probability that the man 
    (II-3) is a carrier of the trait. The woman II-4 is affected by the trait, so she must have genotype aa. So expected progeny genotype is Aa or aa. So overall probability of the son to have the disease is 2/3 x 1/2 = 1/3

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