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Karyotyping How the Test is Performed:
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; and then the cells are harvested, stained, and viewed under the microscope. They are photographed to provide a karyotype which shows the arrangement of the chromosomes. Abnormalities can be identified through the arrangement of the chromosomes.
How to Prepare:
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 miscarriage . A bone marrow specimen requires a bone marrow biopsy .
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How it Feels:
How the test will feel depends on the sample procedure, that is, a venipuncture , amniocentesis , or bone marrow biopsy .
Risks:
The risks are related to the procedure used to obtain the specimen.
Why this Test is Performed:
The blood test is usually performed to evaluate an abnormal appearance or development that suggests a genetic abnormality, to evaluate a couple with a history of miscarriages, or to identify the Philadelphia chromosome that is present in 85% of those with Chronic myelogenous leukemia (CML) . The bone marrow test can also be done to identify the Philadelphia chromosome. The amniotic fluid test is done to evaluate a developing fetus for chromosome abnormalities.
Normal Values:
- females 44 autosomes and 2 sex chromosomes (XX)
- males 44 autosomes and 2 sex chromosomes (XY)
Abnormal Results:
Abnormal results may show Down's syndrome , Trisomy 18, Philadelphia chromosome, Klinefelter's syndrome , Turner's syndrome , or other abnormalities.
Additional conditions under which the test may be performed:
Cost:
The estimated cost is $200.
Special Considerations:
Chemotherapy may cause chromosome breaks interfering with normal results.
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