Question

Question 23
The number of pair(s) of sex chromosomes in the zygote of humans is

(a) One
(b) Two
(c) Three
(d) Four

Answer 1

(a) One

Gametes are formed by the process of meiosis and hence carry only one type of each chromosome. 22 autosomes and either an X chromosome or a Y chromosome (22, X/Y). While an ova can have only an X chromosome the sperm can carry either an X or a Y chromosome.

Zygotes, on the other hand, have two copies of all chromosomes. Sex chromosomes present, without exception, can be either XX or XY (46, XX/XY) (one pair). While an XX carrying zygote will form a female, an XY carrying zygote will give rise to a male.