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Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYPrinciples of Inheritance and Variation1 Mark
MCQ
For question two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion : $Y$ chromosome causes maleness.
Reason: If the number of $X$ chromosome is more than one, femaleness dominates.
  • A
    Both assertion and reason are true and reason is the correct explanation of assertion.
  • B
    Both assertion and reason are true but reason is not the correct explanation of assertion.
  • ✓
    Assertion is true but reason is false.
  • D
    Both assertion and reason are false.
✓

Answer

Correct option: C.
Assertion is true but reason is false.
In mammals, the presence of a $Y$ chromosome is required for the development of a male sex phenotype. ln contrast, the $Y$ chromosome plays no significant role in sex determination in Drosophila. A $Y$ chromosome is required for maleness, moreover, the presence of a single $Y$ chromosome is sufficient even in the presence of several $X$ chromosomes $\text{(e.g., XXXXY)}$

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