Which of the Following is Not Exhibited Fragile X Syndrome

Question

Which of the following is not exhibited Fragile X syndrome?
A) An X chromosome which contains up to 1000 copies of the CCG repeat at one site
B) Inherited mental retardation
C) A correlation between the number of repeats and the severity of the defects
D) The phenomenon of "anticipation"
E) Decreasing numbers of the CCG repeat in successive generations

Accepted Answer

Fragile X syndrome is caused by the expansion of a trinucleotide repeat (CCG) in the FMR1 gene. This repeat can become unstable and increase in size from one generation to the next, leading to the characteristic symptoms of the syndrome. Therefore, decreasing numbers of the CCG repeat in successive generations does not exhibit Fragile X syndrome.