Karyotyping
Chromosome analysisKaryotyping is a test to examine chromosomes in a sample of cells. This test can help identify genetic problems as the cause of a disorder or disease.
How the Test is Performed
The test can be performed on almost any tissue, including:
- Amniotic fluid
Amniotic fluid
Amniotic fluid is a clear, slightly yellowish liquid that surrounds the unborn baby (fetus) during pregnancy. It is contained in the amniotic sac....
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- Bone marrow
- Tissue from the organ that develops during pregnancy to feed a growing baby (placenta)
To test amniotic fluid, an amniocentesis is done.
Amniocentesis
Amniocentesis is a test that can be done during pregnancy to look for certain problems in the developing baby. These problems include:Birth defectsG...
A bone marrow biopsy is needed to take a sample of bone marrow.
Bone marrow biopsy
A bone marrow biopsy is the removal of marrow from inside bone. Bone marrow is the soft tissue inside bones that helps form blood cells. It is foun...
The sample is placed into a special dish or tube and allowed to grow in the laboratory. Cells are later taken from the new sample and stained. The laboratory specialist uses a microscope to examine the size, shape, and number of chromosomes in the cell sample. The stained sample is photographed to show the arrangement of the chromosomes. This is called a karyotype.
Certain problems can be identified through the number or arrangement of the chromosomes. Chromosomes contain thousands of genes that are stored in DNA, the basic genetic material.
How to Prepare for the Test
Follow the health care provider's instructions on how to prepare for the test.
How the Test will Feel
How the test will feel depends on whether the sample procedure is having blood drawn (venipuncture), amniocentesis, or bone marrow biopsy.
Venipuncture
Venipuncture is the collection of blood from a vein. It is most often done for laboratory testing.
Why the Test is Performed
This test can:
- Count the number of chromosomes
- Look for structural changes in chromosomes
This test may be done:
- On a couple that has a history of miscarriage
- To examine any child or baby who has unusual features or developmental delays
The bone marrow or blood test can be done to identify the Philadelphia chromosome, which is found in 85% of people with chronic myelogenous leukemia (CML).
Chronic myelogenous leukemia (CML)
Chronic myelogenous leukemia (CML) is cancer that starts inside the bone marrow. This is the soft tissue in the center of bones that helps form all ...
The amniotic fluid test is done to check a developing baby for chromosome problems.
Your provider may order other tests that go together with a karyotype:
- Microarray: Looks at small changes in the chromosomes
- Fluorescent in situ hybridization (FISH): Looks for small mistakes such as deletions in the chromosomes
Normal Results
Normal results are:
- Females: 44 autosomes and 2 sex chromosomes (XX), written as 46, XX
- Males: 44 autosomes and 2 sex chromosomes (XY), written as 46, XY
What Abnormal Results Mean
Abnormal results may be due to a genetic syndrome or condition, such as:
- Down syndrome
Down syndrome
Down syndrome is a genetic condition in which a person has 47 chromosomes instead of the usual 46.
Read Article Now Book Mark Article - Klinefelter syndrome
Klinefelter syndrome
Klinefelter syndrome, also called 47,XXY, is a genetic condition that occurs in males when they have an extra X chromosome. This can cause problems ...
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- Trisomy 18
Trisomy 18
Trisomy 18 is a genetic disorder in which a person has a third copy of material from chromosome 18, instead of the usual 2 copies. Rarely, the extra...
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Turner syndrome
Turner syndrome is a rare genetic condition in which a female does not have the usual pair of X chromosomes.
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Chemotherapy may cause chromosome breaks that affect normal karyotyping results.
Risks
Risks are related to the procedure used to obtain the sample.
In some cases, a problem may occur in the cells growing in the lab dish. Karyotype tests should be repeated to confirm that an abnormal chromosome problem is actually in the body of the person.
References
Bacino CA, Lee B. Cytogenetics. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 98.
Perle MA, Stein CH. Applications of cytogenetics in modern pathology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 71.
Karyotyping - illustration
Karyotyping is a test used to identify chromosome abnormalities as the cause of malformation or disease. The test can be performed on a sample of blood, bone marrow, amniotic fluid, or placental tissue.
Karyotyping
illustration
Review Date: 10/13/2022
Reviewed By: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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