A phenotypic characterization such as the ones GregorMendel studied. Are your earlobes attached or detached, can you roll your tongue, are your peas smooth or wrinkled.

http://naturalsciences.sdsu.edu/classes/lab2.4/semnet/Mendelian_trait.gif

http://naturalsciences.sdsu.edu/classes/lab2.4/semnet/Mendelian_trait.htm

See PhenotypeTrait, QuantitativeTrait, MendelianGene.

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