Down Syndrome Karyotype - The Most Effective Test For Down Syndrome

Down Syndrome Karyotype – The Most Effective Test For Down Syndrome

By: - Science - August 24, 2011
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If you took a genetics or biology class in high school or college you may recall completing karyotype worksheets when learning about genetics. Karyotype worksheets may have been used to help you learn how chromosomes can vary, producing a variety of genetic abnormalities that can manifest in a range of symptoms. A diagnosis of Down Syndrome, one of these genetic abnormalities, is made by creating a karyotype, or a map of one’s chromosomes. This is typically done through amniocentesis, which removes some of the amniotic fluid from inside the gestational or amniotic sac and analyzes it for chromosomal abnormalities. The number of chromosomes are evident from this map as well as abnormalities in chromosomal structure. A Down syndrome karyotype has an extra chromosome number 21, leaving the individual with 47 chromosomes rather than the normal 46.  In some Down Syndrome karyotypes one can also discover translocations of this same chromosome number 21.

The karyotype “worksheet” generated from the Down Syndrome karyotype testing indicates whether a fetus or individual has Down Syndrome. It indicates the exact number of chromosomes the individual possesses as well as abnormalities such as missing chromosomes, translocations, etc. This is the most thorough method of testing, providing more information than other tests that are available. Essentially, this type of testing provides a “photograph” of the chromosomes on a particular cell.

Unfortunately, while karyotyping is the preferable form of testing for its thoroughness and accuracy, karyotype results can take up to two weeks to be provided to the patient. For a pregnant woman this may be particularly anxiety producing. A Down Syndrome karyotype test can be conducted on a blood sample, which generates quicker results, or by using amniotic fluid. Ultimately, a Down Syndrome karyotype is the most accurate way to determine if an individual or fetus has Trisomy 21 Down Syndrome or translocation Down syndrome. It will also provide information on other genetic defects that may exist.

This type of testing provides a great deal of answers for many people, and allows them to make arrangements and come to terms with the diagnosis should there be an issue with the chromosomes of a fetus. While some people do want to have faster results, the fact of the matter is, the karyotype testing is the most reliable, and as such should be used when it is an option. With more than 25 years of history and use, it is clearly the test of choice for many people.