How does Down Syndrome Occur?
Chromosomes are thread-like structures found in all the cells of our bodies which determine all of our physical characteristics. Chromosomes are composed of genes which contain the material that determines hereditary characteristics and direct all our body functions. Human cells normally contain 23 pairs of chromosomes for a total of 46. Usually one member of each chromosome pair is contributed at conception when each parent-to-be provides reproductive cells (egg and sperm), each containing 23 chromosomes. At conception, the mothers egg and the fathers sperm unite to form a fertilized egg resulting in 46 chromosomes. The first cell goes on to divide to form new cells. These new cells undergo a continuous series of divisions, eventually giving rise to all the cells necessary to form a new human being. After birth, a blood sample is taken from a baby suspected of having Down syndrome for chromosomal analysis.
