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Why Can I Roll My Tongue?

 

Why can I roll my tongue?  Genetic counselors are one group of professionals who are equipped to answer questions like this.  They provide information about certain genetic traits or conditions, and help families adapt to the medical and social aspects of genetic diseases.  Kaylee Henson, a genetic counselor and member of the Indiana Network of Genetic Counselors (INGC), explains what we know about tongue rolling and how genetics may be involved…
 
Initially, the ability to fold or roll the tongue was thought to be simple, single gene genetic trait.  Humans have 23 pairs of chromosomes, for a total of 46 in each cell.  For each pair, we receive one copy from our mom and one copy from our dad.  Each chromosome is made of DNA, which can be broken into smaller sections called genes.  Genes are the instructions that tell our body how to function, like a recipe.  Most genes have two or more variations, which are called alleles.  If someone inherits a copy of the dominant version of the allele, they will have or express that trait, even if the recessive allele is also present.
 
Alfred Sturtevant, a scientist in 1940, published an observational study where he concluded that parents who can roll their tongue will most likely have children that can roll their tongue.  In other words, if you inherited one or two copies of the dominant “tongue rolling gene” (R) allele from your parents, then you would be able to roll your tongue.  If you inherited two copies of the recessive “tongue rolling gene” (r) allele instead, then you would not be able to roll your tongue.  Allele inheritance is most simply demonstrated in a Punnett square, like this one: 
 
 
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The problem with Sturtevant’s study was that sometimes two parents who couldn’t roll their tongue had a child who could!  Sturtevant suggested tongue rolling is at least partially genetic, but more recent studies of families and twins have suggested that tongue rolling is likely much more complicated than previously thought—perhaps it involves multiple genes or the environment plays a role!
Discover more "curioddities" when The Science of Ripley's Believe It or Not® returns to the museum this September! 
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