Researchers examine reason for human 'sweet tooth'

• The researchers created mice with the same sweet-tooth preferences as humans by inserting the gene that codes for a human sweet-taste receptor protein into the animals.
• They also inserted an entirely different receptor gene into the taste cells of mice, thereby producing animals that perceive a previously tasteless molecule as sweet.
• Both of these experiments demonstrate that receptor molecules on the tongue for both the sweet and "savory" umami tastes are what triggers taste cells on the tongue and palate to transmit taste signals to the brain.
• The researchers said their findings open the way for tracing the circuitry for sweet and umami tastes all the way to the centers in the brain that perceive those tastes.