Question

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

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

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

Correct option (c)

Explanation:

Chromosomal or allosomic determination of sex is based on heterogamety or occurrence of two types of gametes in one of the two sexes. Male heterogamety is found in allosome complements XX-XYandXX-XO.

In birds and some reptiles, both the sexes possess two sex chromosomes but unlike human beings, the females contain heteromorphic sex chromosomes (AA + ZW) while the males have homomorphic sex chromosomes (AA + ZZ).