Fragile X Syndrome
Fragile X syndrome develops from an abnormal number of CGG repeats [3]. These repeats are an important factor in determining how the FMR1 gene will be transcribed in the nervous system [3]. Scientists use have used the polymerase chain reaction (PCR) to find that while approximately 29 repeats yield a normal result, over 200 repeats of CGG cause fragile X syndrome [3]. When an excessive number of repeats occurs, normal translation does not, and certain neuronal messages are unable to be carried to the ribosome for translation, causing the symptoms of this disorder.
The X chromosome of people with Fragile X is unusually fragile at one tip and is often described as “hanging by a thread” when viewed under a microscope.
Normal Karyotype
Karyotype of a person with Fragile X
( http://www.biology.iupui.edu/biocourses/N100/2K2humancsomaldisorders.html)
Males are more likely to be inflicted with Fragile X Syndrome because it is, as indicated by the name, a recessive, X-linked mutation. Therefore, females must inherit two copies of the abnormal chromosome in order to have Fragile X Syndrome, while males only need one copy [4].
Physical indicators of this disease include the presence of a large head, long face, prominent ears, and enlarged testicles. These facial characteristics are more common in males with the disease than females. Fragile X Syndrome is the most prevalent form of inherited mental retardation [3].
