Cytogenetic laboratories provide microscopic studies of human chromosomes in order to diagnose abnormalities in prenatal/postnatal and cancer specimens. The studies involve analyzing chromosomes found in blood, bone marrow, amniotic fluid, chorionic villi and tissues using microscopes with computer controlled displays. Some cytogenetic labs also utilize FISH testing which test the more stable DNA. FISH testing can be used on metaphase and interphase cells. A physician normally draws the least amount of specimen that is sufficient to perform a cytogenetic study and sends it along with a requisition sheet to the laboratory. In the lab, the cells are cultured to the point of multiplication and are then harvested. A fluid that makes the cells larger is introduced so that the chromosomes are easily identifiable when viewed under a microscope. The chromosomes are microscopically analyzed in great detail by laboratorians who are trained to look for structural or numerical abnormalities. Finally, the results are submitted in a written report to the physician.

Chromosomes contain all of the genetic material that makes up an individual. They are comprised of DNA and are found within the nucleus of every living cell. Genes are the hereditary units that occupy specific positions on chromosomes and contain the coded information that determine the physical uniqueness of each human being. The typical human cell contains 46 chromosomes. Normally, 23 come from the father and 23 come from the mother. Occasionally, during conception, numerical or structural abnormalities may arise. In the case of cancer, structural and numerical abnormalities arise in conjunction with the disease. GAI also utilizes fluorescent in situ hybridization, which test the more stable DNA structure. FISH testing can be used on metaphase and interphase cells. A fluorescent probe is allowed to attach to a specific region of interest. After this procedure, a fluorescent microscope is incorporated. The areas will fluoresce a particular color and valuable information is obtained.

The following list of common abnormalities may help you to understand chromosome analysis:

Numerical Abnormalities
Numerical abnormalities involving chromosomes in prenatal/postnatal/constitutional or cancer cytogenetics. Upon analysis, when a metaphase exhibits a gain or a loss of a chromosome, this finding is referred to as a numerical abnormality. One of the more common numerical abnormalities seen in prenatal/postnatal cytogenetics, for example, is Down Syndrome (trisomy 21). As seen in the picture at right, there is an extra chromosome 21, indicating this syndrome.

Structural Abnormalities
Structural abnormalities involving chromosomes in prenatal/postnatal/constitutional or cancer cytogenetics. Chromosomes can be seen with structural abnormalities. They can have extra chromosomal material, loss of chromosomal material, areas on chromosomes that break easily, and areas that for some reason have duplicated. A chromosome can be inverted and can also translocate to another chromosome. In cancer cytogenetics, any abnormality or combination of abnormalities is possible. One of the most common structural abnormalities in cancer, for example, would be a translocation involving chromosomes 9 and 22. This translocation (seen at right) is referred to as a Philadelphia translocation.

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The information gained through cytogenetic testing arms the physician with information needed to prescribe the right course of treatment. The following are some of the conditions that necessitate cytogenetic test:

	Pregnant women Advanced maternal age - over the age of 35 Personal history of spontaneous abortions (miscarriages) Family history of genetic abnormalities (Down, Turner, Pateu, Edwards Syndromes, etc.) Abnormal Triscreen results
	Newborn babies Suspicious or questional phenotypic traits Ambiguous genitalia
	Toddlers and Children Suspicious or questionable phenotypic traits Lack of normal physiological development Autism
	Cancer or Suspected Cancer Patients Solid tumors Anemia Leukemia Lymphoma Myelodysplastic Syndrome Myeloproliferative Disorder Testing for successful bone marrow engraftment Suspected breast cancer - HER-2/neu related

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