Do you have Fragile X, or know anyone with the syndrome?

Question

I just found out this is the leading cause of inherited developmental disability - and I'd hardly ever heard of it before.

I'm supposed to do up a brochure on the syndrome: cause, common misconceptions, community services, etc.

If you know anything about it, please let me know. I will research all the usual info, but if you can add anything personal - that would be great! Thanks.

Answer 1

Yes, it is the leading cause of mental retardation in the world. It usually effects boys worse then girls. What happens is that there is a promoter region on the X chromosome that is made up of 25 to 50 GCGC base pair repeats in a normal person. These base pairs sit very close together. Now, when you have fragile X, in that same area you have anywhere from 200 to over 1,000 repeats of CGCG  base pairs in that section. When  the RNA go to replicate that region, it recognizes that there is a problem. So, it undegoes something called "methylation." It wraps that part of the DNA up in methyl groups so tight that it compacts the DNA into a thin string that can sometimes be so "fragile" that the tip of the X chromosome can break off. However, even if it remains attached, anything past that region will never be transcribed, like it's not even there anyway.

Now, the reason boys are often affected more than girls is that they only have 1 X chromosome. Sometimes by virtue of having 2 X's, the one good X can create enough of the required proteins to allow for proper brain functions.

So, a mother who has it may no realize it, and her children may have the problem.

Another issue with it is that it also undergoes something called "genetic anticipation." Each successive generation creates more copies of the CGCG mutation. So, a mother with 500 copies may be fine, but her daughter with 750 copies may be effected. The reasons behind the varying expressivity are still being researched.

I'm sorry that I don't have anything personal I could tell you. I'm just a Biologist. I hope I explained it simply enough... it's not exactly easy to explain. Good luck on your brochure!