Thiourea

Quick, easy, and completely safe means to analyse commonly tested genetic traits. Simple taste tests allow students to determine their possible genotypes.
The ability to taste PTC (Phenylthio Carbamide) and Thiourea is a genetically heritable trait that follows basic Mendelian patterns. They both taste bitter to some people. This is a genetic variation which normally occurs in a ratio of 75% who can taste PTC and Thiourea versus 25% of those who cannot.
Sodium Benzoate is a preservative found in many foods. It is also a compound that some people cannot taste. It can taste bitter, sweet, sour or salty depending on your individual genetic makeup. Since the inheritance of tasting Sodium Benzoate is more complicated than straightforward Mendelian genetics, it is not a good trait to use for teaching genetics but demonstrates that we are all very diverse, and that much of our diversity is genetic.
Non impregnated strips can be used as a known or blind control.