Due to my concerns from the recent testing of the use of turnitin.com at my school, I have now making all my work submitted through this service a public resource. This action is in response to my fear that in such an unstable economy, especially for internet companies, turnitin.com may go bankrupt and that my work may distributed or sold without my knowledge or consent. I also believe that much of the effort and work put in to research projects and papers is wasted when only submitted and read by one teacher for the sole purpose of receiving one grade. By making this paper public, I hope to encourage the dissemination of knowledge made possible by the internet . However, in no way do I condone the idea of plagiarism. Intellectual property is something that must be respected, but at the same time made open to all people.
Many may think that Down syndrome is the most common form of genetically inherited mental retardation; however, in actuality, the lesser-publicized Fragile X syndrome is more widespread. Fragile X syndrome is a genetic mutation of the X chromosome in humans that causes very mild to severe mental retardation. Persons with Fragile X syndrome may exhibit certain physical features in
addition to mental impairment, most commonly large ears. At this point, medical science has not yet devised a treatment for this syndrome, but in mild to moderate cases, the symptoms can be treated with certain medications and special education; additionally, Fragile X syndrome can be detected before birth, through genetic testing, (Facts About Fragile X Syndrome).
The level of mental impairment caused by Fragile X ranges from mild learning disabilities and hyperactivity to severe mental impairment and autism. In addition to mental impairment, there are many common physical characteristics associated with Fragile X syndrome. The most common are large and prominent ears, a trait seen in both males and females with the disorder. An elongated face, flat feet, double-joints, and macroorchidism, i.e. enlarged testicles, are also features seen expressed in males with Fragile X syndrome (Facts about Fragile X Syndrome). Other psychological effects include short attention span, tactile defensiveness or negative response to touch, pervasive speech or repetition of words or phrases, and other effects like hand-biting or hand-flapping (Fragile X Syndrome Checklist).
Fragile X syndrome is the result of a defect in the FMR-1 gene, Fragile X mental retardation gene, which causes that portion of the gene to methylate, i.e. the attachment of a methyl group on to the nucleotides of that portion of the DNA. The DNA methyation of this portion of the X chromosome blocks the production of a protein, the FMRP, the Fragile X mental retardation protein (Quick Summary of Fragile X Syndrome). Specifically, this mutation affects the CGG portion of the FMR-1 gene and causes the section to repeat. The number of repeats usually determines the severity of expression of the Fragile X syndrome. As the gene is passed down the number of repeats increases until the defect is expressed (Facts about Fragile X Syndrome). A normal person has about 30 repeats, but persons with mutated genes have 50 or more. Persons with 55-200 repeats are usually referred to as having a permutation of the gene and are thus likely to have children expressing the defect, but not expressing it themselves. But once the number of repeats increases to a number over 200, the person is known to have the full mutation and is then very likely to express the defect (What is the Mutation in FMR1.).
To understand the effects of the lack of FMRP production, scientists have conducted experiments using knockout mice. A knockout mouse is a transgenic mouse with a targeted wild-type allele replaced with a mutant allele (Gilbert 69-70). In this case, the knockout mouse would have a foreign gene incorporated to stop the production of the FMRP protein to provide a model for Fragile X syndrome in humans. The results of an experiment conducted by William T. Greenough, et al, show that the lack of FMRP greatly reduces the amount of protein synthesis that occurs in the synapses of the brain (Greenough). This lack of normal amounts of protein synthesis in the synapses, in turn is believed to result in the lack of mental ability.
Fragile X syndrome is a sex-linked disorder, specifically an X-linked defect, meaning that it is caused by a mutated X chromosome and is thus inherited through the X chromosome, thus, males are more likely to express the defect than are females (Facts about Fragile X Syndrome). This explained by the fact that males inheriting a defective X chromosome should express the defect as they only have one X chromosome, but females inheriting the gene would have a possibility of not expressing the defect because the effects of the defect could be concealed if the female had a normal X chromosome that provided the DNA necessary for normal function. The probability of the expression of the defect, i.e. a person with the Fragile X phenotype, can be predicted using Punnett squares. Assuming that a child has a normal father and a carrier mother, a mother having one defective X chromosome, the child would have a 50% chance of having a defective genotype as a male, and a 50% chance to become a carrier as a female (see fig. 1). If, in addition to the carrier mother, the father has a Fragile X chromosome, a male child should have 50% chance of exhibiting the defect and a female 50% as well with 50% probability of becoming a carrier (see fig. 2). However, if only the father had Fragile X, a male child would have no chance of inheriting the gene, but the female should have a 50% chance of becoming a carrier. Of course, if both parents suffered from Fragile X syndrome all their children would have a Fragile X. However, the expression of Fragile X syndrome is not determined by genotype alone. There are many cases in which males with the Fragile X chromosome or females with two defective X chromosomes do not exhibit any symptoms. Also, many females with only one Fragile X chromosome exhibit all the effects of the syndrome when the number of repetitions of the CGG section is very great. But, expression of the symptoms of Fragile X syndrome is still more common in males than females, occurring in about 1 in 1000 males and 1 in 2500 females (Facts about Fragile X Syndrome).
Recent developments in the past two decades created genetic tests that can determine whether or not a person has the Fragile X chromosome. However, the ability to detect but not treat Fragile X syndrome has raised ethical dilemmas, as people with the Fragile X genotype could be discriminated against. Elementary schools in Colorado and Georgia have had Fragile X testing programs to isolate students with the genetic defect in an attempt to save money, however in the process students found to have the Fragile X gene have been restricted from participating in certain activities. This is problematic because only the presence of the defective gene and not the severity of expression of the Fragile X syndrome. A more extreme example would be discrimination against a child diagnosed with Fragile X did not experience any symptoms, as is the case of 20% of males and 70% of females with the mutation (Andrews 87-90). Nevertheless, genetic testing and early detection can allow parents to put their children in programs necessary to help them function normally in society.
At this point in time, more research must be conducted before Fragile X syndrome is fully understood. However, there are possible treatments currently being researched, including: gene therapy, where normal genes are inserted into brain cells to replace mutant Fragile X genes, gene repair, where proteins are used to repair the mutant DNA, and psychopharmacology, which is the use of medications to alleviate the symptoms of Fragile X syndrome (About Fragile X). Hopefully in the near future, treatments can be devised to cure Fragile X, but as of now all society can do is to help those affected by this condition to contribute and take part in everyday life.
