can someone please tell me what fragile x is please xxxx
No problem.
Incidently, note that whilst it repeatedly says things like "the most common known single-gene cause of autism" in that Wikipedia article, it also says, under Intellectual Development, "When both autism and FXS are present, a greater language deficit and lower IQ is observed as compared to children with only FXS" which implies, well actually explictly states, that Fragile X can exist in seperation to autism, which is strongly suggestive of a correlatory rather than causal link.
Also, note that Autism does not imply Fragile X.
It's a genetic disorder often found in conjunction with autism (some/many believe it to be one of the genetic causes of autism, but I'm not sure that's been conclusively proven (and may just be correlatory rather than causal)).
See http://en.wikipedia.org/wiki/Fragile_X for more info.