Which genotype represents a premutation in Fragile X syndrome?

In Fragile X syndrome, the CGG repeat sequence located in the FMR1 gene is key to understanding the condition. The classification of the number of CGG repeats provides insight into the risk of developing the syndrome.

Individuals with a premutation have between 55 and 200 CGG repeats. This genetic status means they do not typically exhibit the full symptoms of Fragile X syndrome, which are associated with a full mutation of more than 200 repeats. However, those with a premutation can still have elevated risks for transmission of the condition to their offspring and may potentially face related health issues such as fragile X-associated tremor/ataxia syndrome (FXTAS) in adulthood.

Understanding these ranges is crucial for genetic counseling, as it informs both individuals and families about risks, implications for offspring, and the need for further testing or monitoring.