Genetics Associates Inc.

Our focus at Genetics Associates, Inc. is to provide accurate, timely, and state of the art cytogenetic diagnostic services for physicians and their patients. Over the past 19 years, GAI has built a solid foundation backed by a devoted and experienced staff. Annually, we perform over 18,000 cytogenetic tests for clients throughout the United States.

Perhaps your physician ordered cytogenetic testing for you or a member of your family. Cytogenetic testing provides information which aids the physician in prescribing the appropriate course of treatment.

When do you need cytogenetic testing? What does cytogenetic testing involve?

Pregnancy

Newborns

Pediatric/Adult

Cancer

Cytogenetic laboratories specialize in the diagnosis of chromosome abnormalities. Your sample is sent to our lab where the cells are cultured. Culture times vary from one to fourteen days, depending on the type of sample. After the culture period, the cells are treated so the chromosomes are visible. The chromosomes are stained to achieve their characteristic appearance. Next, the chromosomes are examined by a highly-trained technologist at the microscope. The technologist studies the chromosomes for the proper number and appearance. Afterwards, representative cells are photographed and the chromosomes are arranged in a specific order. These images, or karyograms, are then given to a laboratory director. The director looks at the chromosomes along with your clinical information, interprets the findings, and passes them onto your doctor or genetic counselor.

Genes, which determine things such as sex, eye color, and hair color are made of DNA. This DNA is found within the cell in the form of very fine strands. When the cell divides, it packs these strands of DNA very efficiently. These packed units of DNA are the chromosomes. Most people will have twenty-three pairs of chromosomes, totaling forty-six individual chromosomes. Twenty-two pairs of chromosomes (numbered 1 through 22) are called the autosomes. The remaining pair consists of two sex chromosomes. Women have two X chromosomes, while men have an X and a Y. The pattern for each chromosome is very specific and should look similar in every patient.

Sometimes during cell division, the chromosomes do not split equally into the new cells. This leads to either an extra or a missing chromosome in the cell. Missing a chromosome (monosomy) or having an extra chromosome (trisomy) can cause problems. An example of monosomy is Turner syndrome, in which there is only a single X chromosome. Down Syndrome is a common trisomy, which results from an additional chromosome 21.

Other times, especially in cancer, the chromosomes can break and lose a piece. This is called a deletion. Sometimes, two or more chromosomes break and switch pieces. This is known as a translocation.

Many of these chromosome problems are well-described in medical journals compiled from other patient data. With this information, our directors can give your doctor an idea of your prognosis.

Some abnormalities can be inherited and may require additional testing on you or other family members. Your doctor, or a genetic counselor, can help determine if other family members should consider being tested.

Fluorescence in situ Hybridization or FISH, as it is frequently called, is a special test your doctor orders in addition to your chromosome study. FISH uses small pieces of commercially-prepared DNA called probes. The probes have a fluorescent dye attached to them. These probes can attach (or hybridize) to the corresponding DNA in the cells. Using fluorescent microscopes, the dye can be seen either in the cell or on the chromosomes themselves. This test can determine the number of copies of a gene or chromosome region in each cell. Also, this test can be used to see if two genes on separate chromosomes are translocated.

Microarray, also known as array comparative genomic hybridization (aCGH), is a new technology. Patient DNA is labeled with one color dye, and normal control DNA is labeled with a different color dye. These DNAs are mixed with each other. The mixture of labeled DNA is then hybridized to a slide covered with thousands of probes. If there is an unequal amount of DNA in a particular region, one color will show up more than the other. A special machine is used to analyze these thousands of tiny probe spots and looks for differences in color. If there is something suspicious on the microarray, FISH testing will then be performed to confirm the findings. These results are then interpreted by our directors and given to your doctor.

The information provided by Genetics Associates, Inc. (GAI) is intended only as supplementary information. It is not intended to be used as a substitute for consultations with the healthcare providers that are familiar with your medical needs and is not for use as medical advice.

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