Karyotyping

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Karyotyping

Karyotyping is a test to identify chromosome abnormalities as the cause of malformation or disease. This test can:

• Count the number of chromosomes
• Look for structural changes in chromosomes

The results may indicate genetic changes linked to a disease.

Chromosome analysis

The test can be performed on a sample of blood, bone marrow, amniotic fluid, or placental tissue.

Chromosomes contain thousands of genes that are stored in DNA, the basic genetic material. The specimen is grown in tissue culture in the laboratory. Then, the cells are harvested, and the chromosomes are stained and viewed under the microscope. They are photographed to provide a karyotype, which shows the arrangement of the chromosomes.

Certain abnormalities can be identified through the number or arrangement of the chromosomes.

There is no special preparation for the blood test. To test amniotic fluid, an amniocentesis is performed. Testing on placental tissue is done after a chorionic villus sampling or after a miscarriage. A bone marrow specimen requires a bone marrow biopsy.

For infants and children:

The preparation you can provide for this test depends on your child’s age, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics:

• Infant test or procedure preparation (birth to 1 year)
• Toddler test or procedure preparation (1 to 3 years)
• Preschooler test or procedure preparation (3 to 6 years)
• Schoolage test or procedure preparation (6 to 12 years)
• Adolescent test or procedure preparation (12 to 18 years)

How the test will feel depends on whether the sample procedure is venipuncture (having blood drawn), amniocentesis, or bone marrow biopsy.

The blood test is usually performed to evaluate a couple with a history of miscarriages or to evaluate an abnormal appearance of the body that suggests a genetic abnormality. The bone marrow or blood test can be done to identify the Philadelphia chromosome that is present in 85% of those with chronic myelogenous leukemia (CML). The amniotic fluid test is done to evaluate a developing fetus for chromosome abnormalities.

Review Date: 04/20/2005
Reviewed By: Neal Sondheimer, M.D., PhD., Division of Genetics and Metabolism, Children's Hospital of Philadelphia, Philadelphia, PA. Review provided by VeriMed Healthcare Network.