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NEETZoologyPrinciples of Inheritance and Variation

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In birds, the sex of the offspring is determined by the type of ovum that is fertilized by the sperm. Reason (R): Birds exhibit female heterogamety (ZW type) where females produce two different types of gametes. In the light of the above statements, choose the most appropriate answer from the optio

Options

  1. ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
  2. BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A)
  3. CAssertion (A) is true but Reason (R) is false
  4. DAssertion (A) is false but Reason (R) is true

Correct answer

A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)

Step-by-step solution

In birds, the sex determination mechanism is of the ZZ-ZW type. Females are heterogametic, meaning they possess one Z and one W chromosome and produce two different types of ova (50% carrying the Z chromosome and 50% carrying the W chromosome). Males are homogametic (ZZ) and produce only one type of sperm (all carrying the Z chromosome). Because all sperms are identical with respect to sex chromosomes, the sex of the offspring is determined by the type of ovum (Z or W) that is fertilized by the sperm. Thus, both As

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