Genetic Testing FAQ

Parents often ask us questions about genetic testing and whether or not it is possible their son has already been tested. The following are the questions we are asked the most often, and answers from Dr. Nicole Tartaglia.

Q. What is the name of the test that would be used to detect the extra X & Y chromosomes? How would it appear on the test results?

A. High resolution chromosome testing

Q: Does an amniocentesis include testing for extra X & Y chromosomes?

A: Yes, an amniocentesis looks at the karyotype, so they will see if there is an extra X and/or Y chromosome.

Q. What should be done if an amnio was done years ago, didn’t show extra X & Y chromosomes, but there still isn’t an answer to the child/man’s problems?

A: If an older adolescent or adult had an amnio with normal chromosomes but still has problems of unknown etiology, see a geneticist to review the previous testing to see if any updated techniques may be helpful in evaluation the etiology of the problem. The geneticist may determine if other specific testing needs to be done.

Q. If a Fragile X test was done, would they have looked for extra X & Y chromosomes at the same time?

A: Most of the time, when doctor sends a genetic work-up for Fragile X, they also send a karyotype test. But, this is not always the case. Parents should be sure that the karyotype for their son has been confirmed to be 46, XY and that the Fragile X DNA test has been sent. There have been cases where doctors submitted the Fragile X DNA test, but not the karyotype and the lab did not identify the genetic abnormality.
An extra Y chromosome is never found on a Fragile X test, because they are looking at a gene on the X chromosome in Fragile X. So a boy with XYY or XYYY could go undetected.

Q. Does the High Resolution Chromosome Testing/Karyotype also detect deletions and duplications on the X & Y chromosomes?

A. Large deletions or duplications will show up through this testing, but smaller deletions or duplications will not. Another test called the CGH Array , which is not widely used yet, looks at the X & Y chromosomes at a higher resolution and would detect the smaller deletions or duplications. CGH Array is a very new test and is not always covered by insurance.

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