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NEET Biology Principle Of Inheritance And Variation Question Bank Sex Determination

  • question_answer
    Based on Lyon's hypothesis, what will be the number of Barr bodies found in a human female suffering from Down's syndrome  [AIEEE 2004]

    A) 0

    B) 1

    C) 2

    D) 3

    Correct Answer: B

    Solution :

    Down?s syndrome is a chromosomal abnormality in humans and is associated with an extra chromosome 21 (i.e. chromosomal formula is 45 + xx = 47), while one of the two x-chromosomes becomes genetically inert and heteropycnotic and forms the Barr body. Hence human female suffering from Down?s syndrome contains (2x - 1 = 1) one Barr body.


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