A Human Karyotype Preparation Animation

Blood is collected from the person being analyzed. The blood is added to a growth medium that also contains a chemical that stimulates mitosis. The cells are allowed to grow in this medium for two or three days at body temperature. Colchicine is added to arrest cell division at metaphase. The arrested cells are transferred to a centrifuge tube. Centrifugation concentrates the cells at the bottom of the tube. Addition of a hypotonic salt solution causes them to swell up and move apart. The lysed cells are prepared, fixed, and placed on a microscope slide. A cell is observed and photographed under the microscope. The part of the photo that shows the cell's chromosomes is enlarged and images of individual chromosomes are cut out. Finally, the images are arranged so that all pairs of homologous chromosomes are horizontally aligned by centromeres. The result is a karyotype diagram of the arrested metaphase chromosomes. This is the karyotype of a normal male.

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