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Karyotyping refers to use of a microscope to examine the size, shape, And number of Chromosomes in a sample of body cells. Extra, missing, Or abnormal positions of chromosome pieces can cause problems with a persons growth, development, and body functions.

In karyotyping, the chromosomes in a cell are stained with a dye to make the bands of each chromosome visible. Banding helps show differences in structure among the chromosomes and helps arrange them into pairs. The chromosomes are then photographed through the microscope. The information also can be entered into a computer that displays a picture (karyotype) of the chromosomes arranged in a specific order, from the largest to the smallest. The picture of all of the chromosomes is enlarged and studied for specific chromosome abnormalities.

Most cells in the body have identical chromosome pairs. However, egg and sperm cells have only 23 chromosomes, and mature red blood cells do not contain any chromosomes at all. Karyotyping can be done on most other cells in the body, but usually it is done on white blood cells (lymphocytes).

A karyotyping test most frequently is done on a blood sample taken from a vein. It also can be done on cells taken from a tissue sample (such as skin or bone marrow), from amniotic fluidor from Chorionic Villus sampling (CVS). For more information, see the medical tests Bone Marrow Aspiration and Biopsy, Amniocentesis or Chorionic Villus Sampling (CVS)

How to Prepare

Discuss with your doctor any concerns you have about the need for the test, its risks, or how it will be done. Complete the medical test information form to help you understand the importance of the test.

Karyotyping may be done on a sample of bone marrow. For more information, see the medical test Bone Marrow Aspiration and Biopsy. If amniocentesis or chorionic villus sampling is going to be done, you will need to sign a consent form that says you understand the risks of the procedure and...
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