Insertion (DNA Mutation) — Definition & Examples

Fragile X Syndrome (FXS) is an inherited genetic disorder that causes varying degrees of developmental delay, intellectual disability, and behavioral problems.

We still don't know exactly what causes it, but people with fragile X syndrome have an increased number of CGG repeats in the FMR1 gene. Normally, there are between 5-40 CGG repeats in this gene, but in people with FXS, this sequence is repeated over 200 times.