Question

Assertion: XX - XY type of sex determination mechanism is an example of male heterogamy.

Reason: In birds, male heterogamy is seen, as males produce two different types of gametes.

• 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
• C. Assertion is true but reason is false
• D. Both assertion and reason are false

Answer 1

The correct option is C Assertion is true but reason is false

In humans, males form two types of gametes. One gamete possesses X chromosome and other lacks it. In some cases male may possess a Y chromosome. Such males are known as heterogametic. Females in such cases form only one type of gamete which contain X chromosome.
An X chromosome from female and an X chromosome from male will yield a genetic female, while an X chromosome from female and a Y chromosome from male will yield a genetic male. This is called a XX- XY sex determination system and is an example of male heterogamy.

In many birds, two different types of gametes in terms of the sex chromosomes are produced by females (female heterogamy). Female has a pair of dissimilar chromosomes ZW and male two similar ZZ chromosomes.