Abstract

Genetic diseases are disorders caused by a defect in the DNA sequence, these disorders are inherited because they are in human sexual cells, and sexual cells are responsible for transmitting genetic traits and information from parents to children. Genetic disorders may also sometimes occur due to a DNA sequence defect in physical cells. Genetic diseases: single gene disorders, chromosome disorders 
Fragile x syndrome it's also called martin-bell syndrome, it is X- linked dominant inheritance. It is caused by mutation on fmr1 gene that produced protein gene (fmrp), this disorder effect on chromosome X on the long arm at 27.3 regions. It is more common in males than females, because it is linked to X chromosome, and we can describe this syndrome by two ways, premutation with 55-200 duplication in triple codon CGG on 5` band, or full mutation with more than 200 duplication in triple codon CGG. until now there is no specific treatment, however there might be a treatment by using the physical and behavioral symptoms or by genetic therapy, these ways are for therapy that can improve patient health. This condition causes several problems, including learning difficulties and cognitive impairment, not only to the central nervous system but also to other physiological imbalances. Distinctive physical qualities are more pronounced as they age, including long face, large ears, prominent jaw and flat feet. In males, the testicles swell after puberty. In addition, not everyone with the syndrome has the same symptoms. The syndrome accounts for half of the mental retardation associated with X-chromosome and is the second most common cause of mental disability after Down syndrome. The first case was discovered in 1938 
Meaning of: 
Fmrp = fragile mental retardation protein
fmr1= fragile mental retardation protein