November 23, 2010
Human Genetics Fall 2010
Name of Disorder:
The disease I chose to do research on is called Fragile X Syndrome (FXS). There are a few other names this disease is also known by, such as: Mental retardation, X-linked, associated with marXq28, X-linked mental retardation, macroorchidism, Marker X syndrome, and Martin-Bell syndrome.
The disease is located on the X chromosome located about 27.3 centimorgans. This is expressed as Xq27.3.
Type of Inheritance:
The mode of inheritance of Fragile X Syndrome is X-linked. Women have a fifty percent chance of giving Fragile X Syndrome to their offspring whether it is the pre ...view middle of the document...
Most physical characteristic typically are shown by the age of 8. The behavioral characteristics include: ADD, speech disturbances, hand biting, hand flapping, autistic behaviors, poor eye contact, unusual responses to various touch, and auditory or visual stimuli. Characteristics shown in males are very similar to those shown in females; however, females have a milder intellectual disability and presentation of behavioral and physical characteristics. Only about one third of females show significant intellectual disabilities. Only about twenty five percent of females are affected with the full mutation type of FXS. With individuals with FXS, the probability of seizures is increased. Males have about a fifteen percent chance while females have less than five percent. The risk of epilepsy onset seems to be a lot higher in early childhood with a peek in ages 6 months to 4 years of age. Recurrent seizures could be a strong indicator of the increase for autism along with FXS due to the rate of being 3 time more likely for those individuals.
Fragile X Syndrome is caused by the FMR1 gene not working properly or at all in some cases. "This gene encodes the FMRP protein, which control the availability to select proteins involved in neuron-to-neuron communication," Ascribe Newswire, 2005. The neuron-to-neuron communication happens in the synaptic connections. Fragile X Syndrome patients have a tendency to breakdown this down more rapidly than people not affected with Fragile X Syndrome. The breakdown is caused by an increase in activity in the metabolic glutamate receptor (mGluR), which is located on the surface of the neurons. Studies have found that the overactivity of mGluR could be the cause of many of the symptoms of FXS. The children who are affected with FXS, their X chromosomes look like they were pinched.
The FMR1 gene is composed of the DNA sequence of cytosine, guanine, guanine or CGG. People who are not afflicted with FXS have an average of 29-30 CGG repeats. However, individuals who have inherited FXS have an expanded number of CGG repeats which can range from 50-200 repeats but is classified as a "pre mutation carrier" of FXS. More than 200 CGG repeats results in the "full mutation" FXS. Usually full mutation individuals have anywhere from several hundred to several thousand CGG repeats. Individuals with the full mutation FXS, their FMR1 gene shuts down causing the production of FMRP.
At this time there is no cure for Fragile X Syndrome. There are only ways to help alleviate the symptoms associated to FXS. Special education, speech/language therapy, occupational therapy and behavior therapists become very helpful to those suffering with behavioral and cognitive issues from Fragile X Syndrome. Medications are helpful to those who experience aggression, anxiety, hyperactivity, and who have poor attention spans. It is very important to evaluate each and every individual’s...