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From: Dennis Drayna
Date: 17 Oct 2011
Time: 14:56:27 -0500
Remote Name: 165.112.47.66
Dear Tom - Thanks for these very good questions. To date, we're not seeing significant differences in severity between individuals who carry different mutations and surprisingly, we're also not seeing much difference between individuals in large Pakistani families who carry one copy of a stuttering mutation and those who carry two copies (one on each chromosome). This is quite consistent with a longstanding problem in genetic studies, which has been the inability to identify a specific mode of inheritance (either dominant or recessive) in families. In addition there doesn't seem to be a significant difference we can find between those who stutter due to a genetic mutation and those who have no family history and no identifiable mutation. We only enroll persistent stutterers in our study so we have a substantial ascertainment bias, but it makes sense that carrying a genetic mutation, which is a lifelong trait, is associated with persistent stuttering.