|MadSci Network: Genetics|
When I read the question, I was in the same camp as your partner, but thought that tongue curling may be a recessive trait (which could explain your child’s talent). So I looked around for information on this, and found a surprising answer: Tongue curling is not a simple genetic trait. There has not been a lot of research done on this, but the evidence that exists strongly indicates that this is not a simple genetic trait. Most convincing is a study done by Philip Matlock in 1952 that finds just over 20% of identical twins in the study (7 out of 33) are discordant for this trait. That means one twin can curl their tongue while the other cannot. Another study by N. G. Martin (J. of Heredity 66:179-180, 1975) found that 29% (8 out of 28) of identical twins are discordant for this trait. Disturbingly, I found several web sites that proclaim matter-of-factly that the ability to curl ones tongue is a simple dominant trait. I remember, as do my colleagues, reading this very thing in biology textbooks. This looks like a case of “well everybody knows that, it must be true”. So, your partner is incorrect about tongue rolling, but don’t be too hard on him, he probably learned it in school! I found only one tenuous reference for tongue folding (Hsu, T. C. : Tongue upfolding: a newly reported heritable character in man. J. Hered. 39: 187- 188, 1948.) that apparently describes tongue folding as a recessive trait. Recessive traits can skip generations, and the people who do not show the trait can be “carriers”. That means two people who can’t fold their tongue could have a child who is able to fold their tongue. Here’s a couple web sites that summarizes the data: http://www.people.virginia.edu/~rjh9u/tngrolno.html http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?cmd=entry&id= 189300#189300_Reference7 I hope this relieves the conflict. Alex
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