MP Board · Class 10 · Science · Heredity and EvolutionExplain the mechanisms of sex determination in human beings with the help of a detailed diagrammatic representation or description. How is the sex of a newborn child determined genetically?

Introduction to Sex Determination in Humans\nSex determination is the process by which the sex of an organism is established based on its genetic makeup. In human beings, the sex of the newborn is completely determined by the genetic contribution made by the father.

Chromosomal Basis in Humans

• Total Chromosomes: Human cells contain 23 pairs of chromosomes (46 chromosomes in total).
• Autosomes: Out of these, 22 pairs are common in both males and females, known as autosomes.
• Sex Chromosomes: The 23rd pair consists of sex chromosomes, which differ in males and females:
  • Females possess two identical sex chromosomes represented as XX.
  • Males possess a mismatched pair of sex chromosomes represented as XY.

Mechanism of Genetic Determination

1. Gamete Formation in Females: Women produce only one type of egg (ovum) containing 22 autosomes and one X chromosome (22 + X).
2. Gamete Formation in Males: Men produce two types of sperms in equal proportions: one type containing 22 autosomes and an X chromosome (22 + X), and the other type containing 22 autosomes and a Y chromosome (22 + Y).

Fertilization and Inheritance

• If an egg is fertilized by a sperm carrying an X chromosome: The resulting zygote will have the XX combination (22 + 22 + XX = 46), and it will develop into a female child.
• If an egg is fertilized by a sperm carrying a Y chromosome: The resulting zygote will have the XY combination (22 + 22 + XY = 46), and it will develop into a male child.

Conclusion\nThus, it is evident that the sex of the child is determined by the type of sperm that fertilizes the egg. Since males produce two different types of sperms (X and Y bearing), the father is solely responsible for determining the sex of the child, completely refuting the age-old societal belief blaming mothers for bearing female children.