Why do we taste?

Evaluate nutritious content of food Prevent the ingestion of toxic substances

Why do we taste? What can we taste?

Mammals are believed to distinguish only five basic tastes:

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”

Sweet: Umami: Salt: Sour and bitter:

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

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

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

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

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

Taste test: Phenylthiocarbamide (PTC)

Phenotype: Strong taster __________ Weak taster__________ Non-taster__________

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

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

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

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

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

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

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

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

Binding of PTC leads to release of intracellular calcium

SNPs - Single Nucleotide Polymorphisms Sequencing revealed 3 nucleotide positions that vary within the human population: NucleotideTaster CodonAA 145CCAP 785GCTA 886GTCV

SNPs - Single Nucleotide Polymorphisms Sequencing revealed 3 nucleotide positions that vary within the human population: NucleotideTasterNontaster CodonAACodonAA 145CCAPGCAA 785GCTAGTTV 886GTCVATCI

SNPs - Single Nucleotide Polymorphisms Sequencing revealed 3 nucleotide positions that vary within the human population: NucleotideTasterNontaster CodonAACodonAA 145CCAPGCAA 785GCTAGTTV 886GTCVATCI A combination of SNPs = haplotype

SNPs - Single Nucleotide Polymorphisms Sequencing revealed 3 nucleotide positions that vary within the human population: NucleotideTasterNontaster CodonAACodonAA 145CCAPGCAA 785GCTAGTTV 886GTCVATCI A combination of SNPs = haplotype

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

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

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

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