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DNA: The Long and Short of It


Over 1600 people visited the ASHG booth at the 2011 USA Science and Engineering Festival on the National Mall. We collected data from visitors for two traits, height and the ability to roll the tongue into a U-shape. By the end of two days, we had collected an impressive dataset.







Red dots-Female; Blue dots-Male

View Larger Graph


*Mouseover questions below to reveal answers.

Why do the two graphs look different?


Tongue rolling is a relatively simple trait, probably controlled by one gene (or just a few). Most people can either roll their tongue or they cannot. The result is a two-column bar graph. Height, on the other hand, is controlled by many genes and is influenced by the environment. It is an example of a complex trait, which appears as a continuously varying distribution across a population.


What other observations can you make about the height graph?


As there were more children than adults at the Festival, we can see that the graph is negatively skewed (longer left tail). We can also see that there are more blue dots on the right tail as males tend to be taller than females.


What observations can you make about the tongue-rolling graph?


A European study in 1940s noted that 70 percent of the population can roll their tongues and 30 percent cannot. Our data show a similar percentage. We can also see that blue and red dots are evenly distributed in both columns, showing that sex does not affect the tongue-rolling ability.


The American Society of Human Genetics, Incorporated

9650 Rockville Pike Bethesda, Maryland 20814 1-866-HUM-GENE (301) 634-7300

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