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Class 7
Chapter 6 Class 7 - Adolescence: A Stage of Growth and Change (Curiosi

6.7 Chromosomes and Sex Determination

Last updated at April 26, 2026 by

What are Chromosomes?

They are thread-like structures that carry genetic information in every human cell .

Key Facts and Examples
  • Human cells contain 23 pairs of chromosomes each.
IMG021

A microscope view of a human cell showing
chromosomes arranged in pairs, related to sex
determination.

Example: Every cell in your body has 46 chromosomes total
  • The 23rd pair are called sex chromosomes specifically.
Example: These determine if baby becomes boy or girl
  • Females have XX chromosomes in the 23rd pair.
Example: Mother's egg always carries X chromosome only
  • Males have XY chromosomes in the 23rd pair.
Example: Father's sperm carries either X or Y chromosome
  • The other 22 pairs are identical in males and females.
Example: Height, eye colour genes are same in both
Male vs Female Chromosomes Chromosome Type Males (XY) Females (XX) 23rd pair XY chromosomes XX chromosomes Sperm carries X or Y chromosome Not applicable Egg carries Not applicable X chromosome only Other 22 pairs Same as females Same as males
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