Studies of these mice have pinpointed a cluster of gene positions on mouse chromosome six that are associated with the tasting of a number of bitter substances. Sure enough, gene mapping revealed a set of the GPCR genes on top of that bitter cluster. The new research may help explain the molecular logic behind the taste system and how it differs from the olfactory system. The olfactory system is designed to recognize a wide range of odors and to discriminate one odor from another. Each olfactory neuron expressing only one of the 1,000 or so olfactory receptor genes.
Taste is a different matter, especially where bitter compounds are concerned.
The important thing is to recognize and reject anything bitter, not to get hung up on distinctions among different compounds. Indeed, experimental evidence indicates that humans are unable to discriminate one bitter substance from another. Interestingly, while olfaction is associated with one receptor per cell, taste is associated with many receptors per cell. Zuker believes that the T2R family of genes represents at least a subset of bitter taste receptors. Sweet Tooth Taste receptor research is not all focused on bitter flavors.