What is the typical carrier frequency for Fragile X in women?

The typical carrier frequency for Fragile X syndrome in women is approximately 1 in 257, which is aligned with choice A. This frequency represents how common it is for women to carry a premutation of the FMR1 gene that can lead to symptoms of Fragile X syndrome in subsequent generations. Understanding this carrier frequency is essential for genetic counseling, as it informs risk assessments for families considering having children or those who may be affected by traits linked to Fragile X.

In contrast, the other options suggest significantly lower or higher carrier frequencies, which do not reflect the established research and epidemiological data regarding Fragile X syndrome. For example, a frequency of 1 in 4000 points to a much rarer occurrence than what is seen in the actual population. Similarly, frequencies like 1 in 55 or 1 in 200 do not accurately capture the statistical trends observed in studies of Fragile X prevalence among women.