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: 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"
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Taste test: Phenylthiocarbamide (PTC)
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Phenotype:
Strong taster __________Weak taster __________Non-taster __________
Tasters: 70%Nontasters: 30%
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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.
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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.
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PTC taste receptor structure
Seven-transmembrane domain G-protein coupled receptor.
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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?
How do we study genotype?What material do we need to start with?
http://www.dnai.org/b/index.html
Amazon - Dancing Naked in the Mind Field
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