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    Question

    Which of the following disorders is caused by

    nondisjunction of sex chromosomes?
    A Cystic fibrosis Correct Answer Incorrect Answer
    B Hemophilia Correct Answer Incorrect Answer
    C Turner syndrome Correct Answer Incorrect Answer
    D Sickle cell anemia Correct Answer Incorrect Answer

    Solution

    Turner syndrome is a genetic disorder caused by the nondisjunction (failure of chromosomes to separate properly) of sex chromosomes during meiosis. It results in a monosomy (45, X), where affected individuals have only one X chromosome instead of two (XX in females). It occurs only in females and leads to symptoms such as short stature, underdeveloped ovaries, and infertility.  (1) Cystic fibrosis – An autosomal recessive disorder caused by mutations in the CFTR gene (not related to sex chromosomes). (2) Hemophilia – A sex-linked recessive disorder caused by mutations in clotting factor genes on the X chromosome, but not due to nondisjunction. (4) Sickle cell anemia – A single-gene mutation disorder affecting hemoglobin, inherited in an autosomal recessive pattern, not due to sex chromosome nondisjunction.

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