Table of Contents
Table of Contents
- Sex Determination
- Decision of Sex of Child by Male
- Use of Punnett’s Square in Sex Determination
- Summary
- What’s Next?
In the last segment of the chapter ‘Heredity and Evolution’, we learnt about the law of independent assortment and law of dominance. In this segment, let us study the sex determination in humans.
What is sex determination?
- A biological system that determines the development of sexual characteristics in an organism is called Sex determination. Punnett square is used to predict the outcome of the offspring of two individuals.
- In the Punnett square, the unique genotype of two different individuals is used.
Punnett square
- Humans require a male parent and a female parent to give rise to a new individual.
- The human germ cells do not have a pair of sex chromosomes. Each child receives one copy from the mother and one from the father. They together make up a pair and thus the natural pair of the chromosomes in a cell is established.
XX chromosome pair
- All females have a perfect pair of sex chromosomes in all their cells. It is called the XX chromosome pair. Each chromosome is named with the letter ‘X’. Both these together make up the 23rd pair of chromosomes.
- The male sex chromosome is also made up of two chromosomes: ‘X’ chromosome and ‘Y’
chromosome.
Sex chromosomes
- The 23rd pair of chromosomes of the female parent is represented as ‘XX’ while the 23rd
pair of chromosomes of the male parent is represented as ‘XY’.
- The egg cell and the sperm cell are sex cells and do not have 23 pairs, that is, 46 chromosomes. They have half the number of chromosomes, one from each pair of autosomes and sex chromosomes.
Sex chromosomes
Who decides the sex of the child?
