A system which decides the sexual characteristics of organisms or offsprings is called Sex Determination. Humans require a male and a female parent for reproduction. The fertilized cell divides repeatedly to form a zygote and later take the form of an embryo.
- The human germ cells have half the number of The child receives one copy from the mother and one from the father. They together make up a pair and the natural pair of the chromosomes in a cell is established.
- All females have a perfect pair of sex chromosomes in their cells. It is called the XX chromosome pair. Each chromosome is named with the letter X. Both these together make up the 23 pairs of chromosomes. The twenty-third pair of chromosomes of the female parent is represented as XX.
- The male sex chromosome is also made up of two chromosomes. One is a normal X chromosome while the other is made up of two short strands represented by the letter Y. The twenty-third pair of chromosomes of the male parent is represented as XY.
- The egg cell and the sperm cell are the sex cells. They do not have 23 pairs, that is, 46 chromosomes. Instead, they have half the number of chromosomes, one from each pair of autosomes and sex.
Sex chromosomes in female and male
Sex cells of humans
Who decides the sex of the child?
- In female egg, both the chromosomes of the sex chromosome pair are X
- In males, the sperm cell can either have an X chromosome in the twenty-third chromosome place or a Y chromosome. It depends on which sperm genotype fertilises the egg
- If the cell containing the Y chromosome fertilises the egg cell, the resultant offspring will be with an XY combination, thus a
- If the sperm containing an X chromosome fertilises the egg, it will result in an XX combination, thus a female
- Thus, the sex of the child is decided by the father, at the time of fertilisation.
Determination of the sex of a child
Summary
| Sex Determination in Humans |
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| Determination of the Sex of the Child |
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