How are features of Fragile X Inheritance unique?

In other genetic conditions, being a carrier of that condition means the individual “carries” the condition, that is, they may pass that condition to other generations but are asymptomatic themselves (not at risk for nor has symptoms of the condition). For most conditions, both biological parents need to be carriers with both passing it on for the condition to be present in their child.

Fragile X is different. In Fragile X, only one of the biological parents needs to have an atypical expansion of CGG repeats in the FMR1 gene to pass on Fragile X. (Check out this short, two-minute video that helps explain how the Fragile X premutation or full mutation is passed on to sons and daughters.)

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