TAKING A CLOSER LOOK: DR. DENNIS DRAYNA on GENETICS & THE CARROLL FAMILY TREE
Even though the mainstream media rarely mentions that Carroll was a person who stuttered, his family history gives credence to the discovery of the genetic link to stuttering. Carroll was born to parents who were first cousins; almost all of their eleven children (three girls and seven boys) struggled with stuttering past childhood. Citing Lewis
Carroll's family lineage, Dr. Dennis Drayna explains how stuttering can sometimes be genetically traced through a family line.
Generally speaking, cousin marriages present a risk for the occurrence of so-called recessive genetic disorders. Recessive disorders are those in which usually asymptomatic carriers of a disease gene produce a child that unluckily gets the bad gene from their mother and the bad gene from their father. Thus, they have no good copies of the gene and they then develop the disease. Most recessive disorders are quite rare, but some are more common.
For example, in the United States, about 1 in 24 individuals is a carrier for the mutant gene that carries cystic fibrosis. Since CF carriers are asymptomatic, occasionally two carriers mate and produce offspring, some of whom may inherit a mutated copy of the gene from both parents, thereby becoming afflicted with CF.
While the Carroll family situation is remarkable, families (with all offspring that stutter) are not unheard of. We’ve found many families in Pakistan in which cousin marriages have resulted in many siblings who stutter. We found a polygamous family in Cameroon, West Africa, in which a local chief had three wives and 22 children. We documented stuttering in 18 of them. So, in general, the genetic factors that contribute to stuttering can exert very strong effects.”
The genetic factors that contribute to stuttering are likely numerous, and they display complex inheritance problems. Thus, the great majority of familial stuttering occurs in small clusters, such as two siblings, a parent and offspring, an uncle and nephew, etc., but not as a clear recessive, dominant or other simple inheritance pattern.
Dr. Dennis Drayna is famous for his work in genetic research, which resulted in the identification of “stuttering genes” for the first time ever. He is currently Scientist Emeritus at the National Institutes of Health and continues his work with the genetics of communication disorders. These newfound stuttering genes compromise nine percent of the cases of stuttering.
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