Principles of Inheritance and Variation Question 195

195. A person with the sex chromosomes XXY suffers from

[1997]

(a) Down’s syndrome

(b) Klinefelter’s syndrome

(c) Turner’s syndrome

(d) Gynandromorphism

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Answer : b

Hints & Solution

(b) Down’s syndrome develops due to trisomy of chromosome number 21. In Turner’s syndrome, the effect appears due to fusion of a gamete without sex chromosome and a gamete with one $X$ chromosome (44 + $X)$. Klinefelter individuals are phenotypically males. The defect appears due to fusion of egg having unreduced sex complement $(A+$ $X X$ ) with a gamete carrying $Y$ chromosome $(44+XXY)$. Gynandromorphism occurs in Drosophila. In such individuals one half of the body shows male characters and the other half shows female characters.



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