These strips can be purchased through general lab suppliers and are used in biology inheritance lessons. PTC stands for Phenylthiocarbamide, the organic compound added to the blotting paper strips.
Students take a strip and place the end on their tongue. People who have inherited two dominant 'taste' genes will notice a horrible taste whereas people who have inherited one dominant and one recessive will notice a slightly bitter taste. People who have inherited two recessive genes will not be able to taste anything noticeable.
Around 70% of people can taste PTC to some degree. Studies have been conducted for many years into the correlation between being unable to taste PTC and having habitual traits, for example being addicted to smoking. Some studies have shown that non-smokers are statistically more likely to be able to taste PTC than smokers.
PTC taste strips should be stored in a clean dry environment.