Transcript Hardy-Weinberg Lab

Hardy-Weinberg Lab
Taste Testing
PTC
 Phenylthiocarbamide
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
Compound contains sulfur
Harmless chemical
 Found
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in Brassica family of plants
Cabbages, brussel sprouts, kale
Gives a slight bitterness
Tasting PTC

Dominant: Tasters
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Find low concentrations of
PTC extremely bitter
Homozygous tasters seem
to have a very low
tolerance
• Find it more bitter than
heterozygous tasters
• Oddity: you can only taste
it if it is dissolved in your
own saliva

Recessive: Non-tasters

Report little or no taste
How does this reflect on role of
alleles?
 Alleles
are different versions of same
gene.
 Gene encodes a protein receptor for PTC
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Found on chromosome 7
 Tasters
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have a gene that encode
Proline, Alanine and Valine at positions 49,
262 and 296
 Non-tasters

have a gene
A, V and I at these three positions
Sodium benzoate
 Poly-unsaturated
fat
 Used in food to inhibit microbial growth
 Works best in an acidic environment
Relation to a person’s fave foods

PTC bitter/Sodium benzoate salty
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Tend to like sauerkraut, buttermilk, turnips and
spinach more than average
PTC bitter/Sodium benzoate bitter
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Tend to dislike sauerkraut, buttermilk, turnips,
spinach less than average
Most common taste groups
 Ranked
in order of most common combos
PTC
Sodium Benzoate
 1. Bitter
salty
 2. Bitter
sweet
 3. Bitter
Bitter
 4. Tasteless Salty
 5. Any other combinations
Lab Methods

Part I: PTC Taste/NonTaste
 Step 1: Place control paper on tongue/chew a
little
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Step 2: Place PTC(blue paper) on tongue
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Negative control: you shouldn’t taste anything
Something to compare the other papers to…
Record what you taste
If you don’t taste anything, chew it a little and record
again
Are you a taster or a non-taster?
Lab Methods…pt 1
 Step
3: Record your PTC data on the
board and collect all class data
 Step 4: Calculate the allele frequencies
and the genotype frequencies of the class
Lab Methods pt 2
 thiourea
 How
many of you can taste one but not
the other?
Lab Methods: Pt 3
 Sodium
benzoate