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

Bihar BoardEnglish MediumSTD 12 ScienceBIOLOGYPrinciples of Inheritance and Variation1 Mark
Question
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.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion : Y chromosome causes maleness.
Reason: If the number of X chromosome is more than one, femaleness dominates.
✓

Answer

  1. Assertion is true but reason is false.

Explanation:

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 (e.g., XXXXY)

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