1. Why do we taste?

2. Why do we taste? • Evaluate nutritious content of food • Prevent the ingestion of toxic substances

3. Why do we taste? What can we taste?

4. What can we taste? Mammals are believed to distinguish only five basic tastes:

5. What can we taste? Mammals are believed to distinguish only five basic tastes: Sweet, sour, bitter, salty and umami (msg) Umami: Japanese for “delicious flavor”

6. Sweet: Umami: Salt: Sour and bitter:

7. Sweet: Identify energy-rich nutrients Umami Salt: Sour and bitter:

8. Sweet: Identify energy-rich nutrients Umami: Recognize amino acids Salt: Sour and bitter:

9. Sweet: Identify energy-rich nutrients Umami: Recognize amino acids Salt: Ensures proper dietary electrolyte balance Sour and bitter:

10. Sweet: Identify energy-rich nutrients Umami: Recognize amino acids Salt: Ensures proper dietary electrolyte balance Sour and bitter: Warn against the intake of potentially noxious or poisonous chemicals

11. Taste test: Phenylthiocarbamide (PTC) Arthur Fox, "The Relationship Between Chemical Constitution and Taste” (Arthur Fox and C.R. Noller) Albert Blakeslee, "Genetics of Sensory Thresholds: Taste for Phenyl Thio Carbamide"

12. Taste test: Phenylthiocarbamide (PTC)

13. Phenotype: Strong taster __________ Weak taster __________ Non-taster __________

14. Phenotype: Strong taster __________ Weak taster __________ Non-taster __________ Tasters: 70% Nontasters: 30%

15. Why do we taste? What can we taste? How can we taste?

16. There are variations in sensitivity to the basic tastes around the tongue.

17. Chandrashekar et al. The Receptors and Cells for Mammalian Taste. Nature. (444) p. 288. 2006.

18. Chandrashekar et al. The Receptors and Cells for Mammalian Taste. Nature. (444) p. 288. 2006.

19. Miracle Fruit - Synsepalum dulcificum Makes everything taste sweet Miraculin - a glycoprotein found in Miracle Fruit can possibly change the structure of taste cell receptors Sweet receptors are activated by acid

20. Bitter taste receptors: - Scientists have identified 30 bitter taste receptors - PTC taste receptor identified in 2003 - Chromosome 7: Single exon - 1002 base pairs Kim, U-K et al. “Positional Cloning of the Human Quantitative Trait Locus Underlying Sensitivity to Phenylthiocarbamide” Science 299 (1221 - 1225). 2003.

21. PTC taste receptor structure Seven-transmembrane domain G-protein coupled receptor.

22. Binding of PTC leads to release of intracellular calcium

23. SNPs - Single Nucleotide Polymorphisms Sequencing revealed 3 nucleotide positions that vary within the human population: Nucleotide Taster Codon AA 145 CCA P 785 GCT A 886 GTC V

24. SNPs - Single Nucleotide Polymorphisms Sequencing revealed 3 nucleotide positions that vary within the human population: Nucleotide Taster Nontaster Codon AA Codon AA 145 CCA P GCA A 785 GCT A GTT V 886 GTC V ATC I

25. SNPs - Single Nucleotide Polymorphisms Sequencing revealed 3 nucleotide positions that vary within the human population: Nucleotide Taster Nontaster Codon AA Codon AA 145 CCA P GCA A 785 GCT A GTT V 886 GTC V ATC I A combination of SNPs = haplotype

26. SNPs - Single Nucleotide Polymorphisms Sequencing revealed 3 nucleotide positions that vary within the human population: Nucleotide Taster Nontaster Codon AA Codon AA 145 CCA P GCA A 785 GCT A GTT V 886 GTC V ATC I A combination of SNPs = haplotype

27. Question: Does your genotype for the PTC receptor correlate with phenotype?

28. Question: Does your genotype for the PTC receptor correlate with phenotype? How do we study genotype? What material do we need to start with?

29. PTC Lab Protocol DAY 1: DNA isolation Waivers / Assign numbers

30. http://www.dnai.org/b/index.html Amazon - Dancing Naked in the Mind Field