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

6.8 Genetic Process of Sex Determination

Last updated at April 26, 2026 by

What is Sex Determination?

It is the genetic process by which baby's sex is decided during fertilisation .

Key Facts and Examples
  • Sex determination happens at the moment of fertilisation .
IMG022

A diagram showing sperm approaching an egg during
fertilization, illustrating the genetic process of
sex determination.

Example: When sperm meets egg, baby's sex is fixed
  • The mother's egg always carries X chromosome only.
Example: All eggs from ovary have X chromosome
  • The father's sperm can carry X or Y chromosome .
Example: Half sperm have X, half have Y
  • X sperm + egg results in XX baby (female).
Example: Girl babies get X from both parents
  • Y sperm + egg results in XY baby (male).
Example: Boy babies get X from mother, Y from father
  • The father determines the baby's sex , not mother.
Example: Sperm type (X or Y) decides the outcome
  • Sex determination is a natural genetic process that should be respected .
Example: Equal chance of boy or girl in each pregnancy
Sex Determination Process Step 1 Egg always has X chromosome Step 2 Sperm has X or Y chromosome Step 3 Fertilisation occurs between sperm and egg Step 4 X sperm creates XX (girl) Step 5 Y sperm creates XY (boy) Baby's sex is determined!

Question (Page Not Specified): How is the sex of the child determined?

Answer:
We have studied that sex chromosomes determine whether a baby becomes male or female . This is why the sperm type decides the outcome.

  • Father's sperm carries either X or Y chromosome
  • Mother's egg always carries X chromosome only
  • X sperm + egg creates female baby (XX)
  • Y sperm + egg creates male baby (XY)
Sex Determination Equations Female Child X Sperm + X Egg → XX Baby + Girl Male Child Y Sperm + X Egg → XY Baby + Boy

🌟 Fascinating Fact: Sex determination is a natural, genetic process that should be respected. It is illegal in India to use medical techniques to determine the sex of an unborn child for non-medical reasons due to gender bias in society. The pre-natal sex determination is considered an offence as per the law.

Legal and Ethical Aspects Natural Process Genetic determination is normal Equal Probability 50% chance boy or girl Legal Protection Sex determination tests banned Social Respect Both genders equally valuable

Section Summary: How is the Sex of the Child Determined?

Sex Determination Complete Picture Chromosomes 23 pairs, 23rd determines sex Female XX Two X chromosomes Male XY One X, one Y chromosome Fertilisation Sperm type decides baby's sex Natural Process Should be respected equally
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