Question

How is sex determined in human beings.

Answer 1

Hint: In humans, sex is determined by sex chromosomes X and Y where XX females and XY male. These chromosomes harbor dramatically different numbers. It's a set of genes . During the early evolution of mammals they originated from ordinary autosomes.

Complete Answer:
- Sex in humans is determined by the type of male haploid gamete that fuses with the female egg. The chromosome in the $23^{rd}$ pair of a male gamete can be either X or Y. The female egg always has an X chromosome.
- When the male gametes with the X chromosome and fuses with the female egg then the child will be female. Similarly when the male gamete with the Y chromosome and fuses with the female egg then the child will be male. Or other word, Human follows XX- XY mechanism of sex determination.
- In which females have forty-six chromosomes arranged in twenty-three homologous means homomorphic pairs. Males have twenty-two homomorphic pairs and one heteromorphic pair means the XY pair.
- All the gametes produced by females contain only the X chromosome (22 A + X) during meiosis and the males produce two kinds of gametes, with $\dfrac{1}{2}$ X-chromosomes and $\dfrac{1}{2}$ with Y-chromosomes it means (22 A + X and 22 A + Y).
- A female child (44A + XX) is the result of fertilization of egg (22 + X) with sperm carrying 22+X chromosomes. male child (44A + XY) is the result of Fertilization of egg (22 + X) with a sperm carrying 22+Y chromosomes.

Note: Sex is determined at the time of fertilisation. A female has XX chromosomes and it produces ova of one type and a male has XY chromosome and produces two types of sperm . If the sperm containing X chromosome fuses with ovum, the individual will be a girl and the sperm containing Y chromosome fuses with ovum, the individual will be boy.