Question

What is the effect of nucleotides on Fragile X Syndrome, an X-linked Dominant disorder?

1) They enhance the expression of the FMR1 gene
2) They reduce the expression of the FMR1 gene
3) They have no effect on the expression of the FMR1 gene
4) The effect of nucleotides on the expression of the FMR1 gene is not known

Answer 1

Nucleotides, through expanded CGG triplet repeats, reduce the expression of the FMR1 gene, playing a role in Fragile X Syndrome by leading to gene silencing.

Step-by-step explanation:

The effect of nucleotides on Fragile X Syndrome, which is caused by mutations in the FMR1 gene, is that they reduce the expression of the gene. In individuals with Fragile X Syndrome, a critical part of the gene termed the CGG triplet repeat is expanded, which leads to the gene being methylated and subsequently silenced. This means that the affected individual's cells produce little or none of the protein that the FMR1 gene codes for. Epigenetic changes, such as DNA methylation, impact gene expression by modifying chromatin structure and altering nucleosome packaging, which can prevent the transcription of the gene. Therefore, the correct answer to the student's question is that nucleotides - specifically in the form of expanded CGG triplet repeats - reduce the expression of the FMR1 gene.