In which Fragile X range may progression to premutation occur in children?

The correct answer is that children may progress to a premutation in the range of 45-55 CGG repeats. In the context of Fragile X syndrome, a premutation typically refers to a range of CGG repeats where individuals may not express full features of the syndrome but can experience associated issues, such as anxiety and mood disorders, and have the potential to pass on the mutation to offspring.

A range of 45-55 CGG repeats is particularly significant as it represents a threshold where individuals carrying these alleles may have an increased risk of transmission instability, leading to further expansion in the next generation. This is a key concern because, outside of this range, carriers of fewer than 45 repeats are considered normal, and those with more than 55 repeats might already be classified as full mutation carriers, which is associated with clinical manifestations of Fragile X syndrome.

Thus, the range of 45-55 is crucial for understanding the genetic counseling implications regarding risk assessment for families, as it signifies the potential for children in this range to have a premutation status leading to larger expansions in their offspring. This information is foundational in genetic counseling as it aids in understanding inheritance patterns of Fragile X.