There are many forms of mental retardation. Webster's New World Dictionary defines mental retardation as "a condition, usually congenital, characterized by subnormal intelligence" (Agnes, p404). Mental retardation can be caused by a certain congenital defect due to a traumatic event during the mother's pregnancy, or it can also be inherited. The most common inherited form of mental retardation is fragile X syndrome. Fragile X syndrome was identified in 1991. This disability affects more males than females. Approximately 1 in 4,000 males are affected, but only 1 in 8,000 females (Lombroso, 2003). Fragile X arises in the FMR1 gene. Fragile X is caused by an excessively repetitive trinucleotide, cytosine-guanine-guanine, found in the FMR1 gene. Regular permutation cells have 29 or 30 triplets. Normal alleles have 5 to 50 repeating cells (Gecz, 111,112). FMR gene 1 cells can repeat up to 200 times. Changes within nucleotides can cause problems with gene transcriptions (Lombroso, 2003). Gene expansions due to excessive repetition can cause physical, neurocognitive, and emotional characteristics (“Defining Fragile X Syndrome, 2002). As stated above, Fragile X is an inherited disability. Fragile X can, however, be passed down in family genes from individuals without signs of fragile X (NFXF, 2004). Fragile X syndrome 4Fragile X is found in both males and females; however, the qualities that females possess in some cases differ from the qualities that males possess. Only half of females will actually show symptoms. Females with Fragile X will appear quiet, shy and often prefer to keep to themselves. One-quarter of females...... half of paper ......understanding fragile X syndrome: insights from animal models,112-113.Lathe, R. (2006). Autism, brain and environment. Autism and autism spectrum disorders: an introduction to the problem of recognition and diagnosis, 20-21.Lombroso, P. (2003). Genetics of childhood disorders: XLVIII. Learning and Memory, Part 1: Update on Fragile X Syndrome. Journal of the American Academy of Child and Adolescent PsychiatryNational Fragile X Foundation (2006). Retrieved January 27, 2009, from http://www.nfxf.org/html/what.htm Fragile X syndrome 9Roberts, J., Long, S., Malikin, C., Barnes, E., Skinner, M. , Hennon, E., et al. (2005). A comparison of the phonological skills of children with fragile X syndrome and Down syndrome. Journal of Speech, Language and Hearing Research 48.5Smith, D (2006). Introduction to special education. Mental retardation 197,202.