|MadSci Network: Genetics|
Well, that's a good question. Most traits that are discussed in High School have a genetic basis that's quite well explained by one gene with influence on the trait. In reality few if any complex phenotypes have ONLY one gene involved in their expression. BUT, often one or a few genes can suffice to explain most or almost all of a phenotype and in the case of the simple examples used in high school, these traits can be considered Mendelian traits- that is traits that are largely determined by one genetic locus and a couple to a few alleles. The genes used in GM crops to confer insect and herbicide resistance are Mendelian because almost all the variability is explained by the presence or absence of the transgene. Most genes aren't like that, especially in people. Examples of traits that are nearly Mendelian in humans are tongue rolling (similar to the Vulcan thing), tasting certain chemicals, and eye color- brown is dominant to blue, so theoretically, blue eyed parents can't produce a brown eyed child. Again, it's not that simple because in reality, for example, blue eyed parents for a variety of unusual reasons rarely CAN produce brown eyed children. And there are green eyed people etc. So, if you are asking if the ability to make that Vulcan sign (the Star Trek gesture was actually derived by Leonard Nimoy from gestures made during Jewish ceremonies) is genetic, it is, but though one locus may be most responsible for the phenotype, there may be more than one locus and possibly multiple alleles at each locus involved.
Try the links in the MadSci Library for more information on Genetics.