Why do we taste?

Why do we taste?

• Evaluate nutritious content of food

• Prevent the ingestion of toxic substances

Why do we taste?

What can 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” (Arthur Fox and C.R. Noller)

Albert Blakeslee, "Genetics of Sensory Thresholds: Taste for Phenyl Thio Carbamide"

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Taste test: Phenylthiocarbamide (PTC)

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

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.

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

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

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

QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.

Miracle Fruit - Synsepalum dulcificumMakes 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 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.

QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.

PTC taste receptor structure

Seven-transmembrane domain G-protein coupled receptor.

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Binding of PTC leads to release of intracellular calcium

SNPs - Single Nucleotide Polymorphisms

Sequencing revealed 3 nucleotide positions that varywithin the human population:

Nucleotide TasterCodon AA

145 CCA P785 GCT A886 GTC V

SNPs - Single Nucleotide Polymorphisms

Sequencing revealed 3 nucleotide positions that varywithin the human population:

Nucleotide Taster NontasterCodon AA Codon AA

145 CCA P GCA A785 GCT A GTT V886 GTC V ATC I

SNPs - Single Nucleotide Polymorphisms

Sequencing revealed 3 nucleotide positions that varywithin the human population:

Nucleotide Taster NontasterCodon AA Codon AA

145 CCA P GCA A785 GCT A GTT V886 GTC V ATC I

A combination of SNPs = haplotype

SNPs - Single Nucleotide Polymorphisms

Sequencing revealed 3 nucleotide positions that varywithin the human population:

Nucleotide Taster NontasterCodon AA Codon AA

145 CCA P GCA A785 GCT A GTT V886 GTC V ATC I

A combination of SNPs = haplotype

Question:

Does your genotype for the PTC receptor correlatewith phenotype?

Question:

Does your genotype for the PTC receptor correlatewith phenotype?

How do we study genotype?What material do we need to start with?

PTC Lab Protocol

DAY 1: DNA isolation

Waivers / Assign numbers

http://www.dnai.org/b/index.html

Amazon - Dancing Naked in the Mind Field