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Question
Assertion (A): ‘XX-XY’ type of sex-determination mechanism is an example of male heterogamety.
Reason (R): In birds male heterogamety is observed as males produce two different types of gametes.
Options
Both (A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(A) is true, but (R) is false.
(A) is false, but (R) is true.
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Solution
(A) is true, but (R) is false.
Explanation:
Sex in humans and many other animals is determined by the XX-XY system. Males are heterogametic because they create two types of sperm, one carrying X and the other carrying Y, due to their XY chromosomes. Females only generate one type of egg (X) since they have XX chromosomes. But in birds, the converse is true; females have heterogametic ZW sex chromosomes, while males have homogametic ZZ sex chromosomes. The explanation is inaccurate because it discusses birds rather than people.
