What is the outcome of having AGG interruptions in the trinucleotide repeats in Fragile X?

Having AGG interruptions within the CGG trinucleotide repeats in the FMR1 gene, which is associated with Fragile X syndrome, plays a crucial role in the stability of those repeats during DNA replication. When AGG interruptions are present, they help to stabilize the CGG repeat sequence, reducing the likelihood of repeat expansion in successive generations. This means that individuals carrying these interruptions are less likely to pass along a larger number of repeats to their offspring, thereby decreasing the risk of the repeats expanding into a range that would lead to Fragile X syndrome or its associated features, such as intellectual disability.

In contrast, the presence of a full or long CGG repeat expansion, without these AGG interruptions, significantly increases the chances of expansion in subsequent generations, consequently elevating the risk of Fragile X mental retardation in children. Thus, the correct choice reflects the protective effect of AGG interruptions against the expansion of the CGG repeats.