What are chromosomes?

Sperms and Ovas are sex cells.

We know that every cell contains nucleus.

Nucleus of cell contains thread like structures called chromosomes

These chromosomes carry genes and help in transfer of characters from parents to children


What are Sex Chromosomes?

We know that when Male sperm meets female ova, fertilized cell is produced

This cell has 23 pairs of chromosomes in its nuclei

Out of these chromosomes, two chromosomes X and Y are called sex chromosomes

They help to determine whether new born child will be a boy or girl


How is sex of baby determined?

Sex of an unborn baby is determined when the egg cells of the women gets fertilized by the sperm cells of man and pregnancy takes place.


Sex chromosomes are present in the nuclei of each cell

Male sperm has 2 chromosomes X and Y

Female egg has 2 chromosomes X and X


When both fertilize,

X Chromosome of Male + X Chromosome of Female → XX Chromosome of Zygote ( Female )

Y Chromosome of Male + X Chromosome of Female → XY Chromosome of Zygote ( Male )

fig 10.4.jpg

So sex of child is dependent upon father not mother (as father has both X and Y chromosome, but mother only has X chromosome)



NCERT Question 8 (c) - Sex determination in the unborn baby.

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CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo