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Human chromosome 16, coloured scanning electron micrograph (SEM). Chromosomes are a packaged form of the genetic material DNA (deoxyribonucleic acid). Each consists of two identical, parallel strands (chromatids, left and right), joined at an area called a centromere (centre, green). The tips (blue) are called telomeres. Humans have 23 pairs of chromosomes. This is chromosome 16, which carries between 850 and 1200 genes. Gene defects on this chromosome are related to diseases such as Crohn's disease and thalassaemia, and may also contribute to obesity. Magnification: x19,500 when printed 10 centimetres tall.
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