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Chromosomes

Where the unique genetic blueprint for your unborn baby is stored.

The genetic make-up of a child is decided at the moment of fertilisation. Each parent contributes a blueprint that determines how your baby grows and develops. This information is stored in the chromosomes. Each cell has 46 chromosomes arranged in 23 pairs. Cells divide to multiply for tissue growth and repair. Before division, a cell’s chromosomes double, so each subsequent cell receives 23 pairs. But doubling does not occur in the sex cells that combine for sexual reproduction. Instead the male and female parent cells with 46 chromosomes divide to form sperms and ova with 23 chromosomes. A sperm and an ovum fuse to produce a fertilised egg with 46 chromosomes, 23 from each parent. So the resulting baby will inherit characteristics from both its mother and father.

A baby’s sex depends upon special chromosomes that it inherits. The cells from the mother include a pair of x-shaped sex chromosomes and the cells from the father include one x and one Y chromosome. A baby inherits only one sex cell from each parent. If the baby inherits two x-chromosomes, it will be female. If it inherits one x and one Y chromosome it will be male.




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