Wednesday, March 18, 2009

Chromosome diseases

Chromosome diseases are genetic diseases where a large part of the genetic code has been disrupted. Chromosomes are long sequences of DNA that contain hundreds or thousands of genes. Every person has 2 copies of each of the 23 chromosomes, called chromosomes 1..22 (or "autosomes") and the 23rd is the sex chromosome, which is either X and Y. Men are XY and women are XX in the 23rd chromosome pair.

The most common type of chromosomal condition is a trisomy condition involving a triplet of chromosomes. Trisomy conditions are chromosome conditions where the disease results from an extra chromosome. Normal humans have two copies of the non-sex chromosomes 1..22, and disease arises if a fetus wrongly gets a third copy of any of these chromosomes.

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