Question

What mutation occurs to the FMR1 gene that causes fragile X syndrome?

1) Deletion of CGG repeats in the FMR1 gene
2) Insertion of CGG repeats in the FMR1 gene
3) Point mutation in the FMR1 gene
4)uplication of the FMR1 gene

Answer 1

Fragile X syndrome is caused by an insertion of CGG repeats in the FMR1 gene, leading to a disruption in the production of a vital protein for neural development.

Step-by-step explanation:

Fragile X syndrome is caused by a mutation in the FMR1 gene, involving the insertion of an abnormally high number of CGG repeats. In unaffected individuals, the FMR1 gene typically has up to 44 CGG repeats. However, in individuals with fragile X syndrome, the number expands to over 200 repeats, resulting in a dynamic mutation. This excessive repetition triggers transcriptional silencing, preventing the production of the FMRP. FMRP is crucial for normal neural development, and its absence leads to cognitive impairments and behavioral challenges associated with fragile X syndrome, a common inherited cause of intellectual disability.