Question

It is thought that when the number of repeats reaches above ______ the CGG regions of the gene become chemically modified so that the bases within and around the repeat are methylated, causing inactivation of the gene.

Answer 1

When CGG repeats within CpG islands exceed a specific threshold, the cytosines are methylated, leading to gene inactivation. The exact number of repeats required for this to occur was not specified.

Step-by-step explanation:

The question relates to the phenomenon of DNA methylation occurring within regions called CpG islands, which are areas with a high frequency of cytosine and guanine pairs. When the number of CGG repeats in these regions exceeds a specific threshold, the cytosines can be methylated, adding a methyl group to them. This process changes the DNA's structure and interaction with proteins, such as histones, which can cause gene inactivation. The precise threshold at which this occurs was not provided, but excessive CGG repeats lead to methylation and silencing of the associated gene.