Hardy-Weinberg LabHardy-Weinberg Lab

Taste TestingTaste Testing

PTCPTC

PhenylthiocarbamidePhenylthiocarbamide Compound contains sulfurCompound contains sulfur Harmless chemicalHarmless chemical

Found in Brassica family of plantsFound in Brassica family of plants Cabbages, brussel sprouts, kaleCabbages, brussel sprouts, kale Gives a slight bitternessGives a slight bitterness

Tasting PTCTasting PTC

Dominant: TastersDominant: Tasters Find low concentrations of Find low concentrations of

PTC extremely bitterPTC extremely bitter Homozygous tasters seem Homozygous tasters seem

to have a very low to have a very low tolerancetolerance

• Find it more bitter than Find it more bitter than heterozygous tastersheterozygous tasters

• Oddity: you can only taste Oddity: you can only taste it if it is dissolved in your it if it is dissolved in your own salivaown saliva

Recessive: Non-tasters Recessive: Non-tasters Report little or no tasteReport little or no taste

How does this reflect on role of How does this reflect on role of alleles?alleles?

Alleles are different versions of same Alleles are different versions of same gene.gene.

Gene encodes a protein receptor for PTCGene encodes a protein receptor for PTC Found on chromosome 7Found on chromosome 7

Tasters have a gene that encodeTasters have a gene that encode Proline, Alanine and Valine at positions 49, Proline, Alanine and Valine at positions 49,

262 and 296 262 and 296 Non-tasters have a geneNon-tasters have a gene

A, V and I at these three positions A, V and I at these three positions

Sodium benzoateSodium benzoate

Poly-unsaturated fatPoly-unsaturated fat Used in food to inhibit microbial growthUsed in food to inhibit microbial growth Works best in an acidic environmentWorks best in an acidic environment

Relation to a person’s fave foodsRelation to a person’s fave foods

PTC bitter/Sodium benzoate saltyPTC bitter/Sodium benzoate salty Tend to like sauerkraut, buttermilk, turnips and Tend to like sauerkraut, buttermilk, turnips and

spinach more than averagespinach more than average

PTC bitter/Sodium benzoate bitterPTC bitter/Sodium benzoate bitter Tend to dislike sauerkraut, buttermilk, turnips, Tend to dislike sauerkraut, buttermilk, turnips,

spinach less than averagespinach less than average

Most common taste groupsMost common taste groups

Ranked in order of most common combosRanked in order of most common combos

PTCPTC Sodium BenzoateSodium Benzoate 1. Bitter1. Bitter saltysalty 2. Bitter2. Bitter sweetsweet 3. Bitter3. Bitter BitterBitter 4. Tasteless4. Tasteless SaltySalty 5. Any other combinations5. Any other combinations

Lab MethodsLab Methods

Part I: PTC Taste/NonTastePart I: PTC Taste/NonTaste Step 1: Place control paper on tongue/chew a Step 1: Place control paper on tongue/chew a

littlelittle Negative control: you shouldn’t taste anythingNegative control: you shouldn’t taste anything Something to compare the other papers to…Something to compare the other papers to…

Step 2: Place PTC(blue paper) on tongueStep 2: Place PTC(blue paper) on tongue Record what you tasteRecord what you taste If you don’t taste anything, chew it a little and record If you don’t taste anything, chew it a little and record

againagain Are you a taster or a non-taster?Are you a taster or a non-taster?

Lab Methods…pt 1Lab Methods…pt 1

Step 3: Record your PTC data on the Step 3: Record your PTC data on the board and collect all class databoard and collect all class data

Step 4: Calculate the allele frequencies Step 4: Calculate the allele frequencies and the genotype frequencies of the classand the genotype frequencies of the class

Lab Methods pt 2Lab Methods pt 2

thiourea thiourea How many of you can taste one but not How many of you can taste one but not

the other?the other?

Lab Methods: Pt 3Lab Methods: Pt 3

Sodium benzoateSodium benzoate