Download Supertaster

hBARSCI “Supertaster” Lab
Are you a “Supertaster?!”
Materials Included:
100 Strips containing Phenylthiourea (PTC)
100 Strips containing Sodium Benzoate
100 Strips containing Thiourea
100 Strips containing NO chemical (Control)
Key Vocabulary:
 Genotype: the specific genes found in DNA.
 Phenotype: the physical expression of genes (examples: eye color; tasting ability).
 Heredity: the passing of genetic information from parent to offspring.
 Punnett Square: a method for determining the qualitative chances of offspring
inheriting certain genes from their parents.
Introductory (Pre-Lab) Information:
Mammals, such as humans, have a unique sense that makes consuming certain
substances pleasant and consuming other substances unpleasant – the ability to taste. Special
receptors in the taste buds on our tongues allow us to taste five different flavors – sweet, salty,
bitter, sour, and umami (savory). Without this ability, Brussel sprouts would taste exactly the
same as cupcakes! Not only does taste make consuming food more interesting, but it also
serves a purpose – it allows humans to determine the relative safety of what they plan to
consume. Toxic substances tend to be bitter in taste, so humans tend to avoid this particular
flavor – not only do most people find this taste unpleasant, but they also have an aversion to it
for evolutionary reasons – it can signify danger!
Just as humans have different levels of acuity in the senses of smell and sight, they also
have differences in their ability to taste. Approximately 25% of Americans are considered
“supertasters” and, of this subset, people have varying levels of “supertasting” ability.
“Supertasters” are people who have the ability to taste the substance Phenylthiourea (PTC).
Some people cannot taste this substance at all and others taste it quite distinctly. Whether or
not a person is a supertaster (phenotype) is dependent on his/her genetics (genotype). For the
purposes of this experiment, the dominant supertasting gene will be represented as “S” and the
recessive supertasting gene will be represented as “s.” Based on the genetics involved, there are
four basic types of tasters  normal tasters (no S or s), standard supertasters (__ s), recessive
supertasters (ss), and dominant supertasters (S__):
Copyright 2015, hBARSCI LLC
Label
Genotype
Phenotype
Normal Taster
___ ___
Standard
Supertaster
Recessive
Supertaster
Dominant
Supertaster
__ s
Cannot taste any difference amongst the
substances
Can taste PTC
ss
S __
Can taste PTC and Thiourea, but not Sodium
Benzoate
Can taste PTC, Thiourea, and Sodium Benzoate
To further understand how these genotypes (genes found in DNA) express as
phenotypes (gene expression (as differing levels of taste, in this experiment)) and to better
understand how these genes work in heredity (passing genes from parent to offspring), see the
following Punnett squares that represent various pairings of parents with non-supertaster and
supertaster genes:
___
___
___
___ ___
___ ___
When 2 Normal Tasters (that have NO
supertaster genes) have a child, the percentage
chance of having a supertaster (dominant or
___
S
___ ___
___ ___
recessive) is 0%.
S
S
When 2 Dominant Supertasters (that each have TWO
SS
SS
dominant supertaster genes (SS)) have a child, the
percentage chance of having a dominant supertaster (S __) is
100%. The percentage chance of having a standard supertaster
S
SS
SS
(__s) is 0% and the percentage chance of having a recessive
supertaster (ss) is also 0%.
Copyright 2015, hBARSCI LLC
S
S
____
SS
S ___
When 2 Dominant Supertasters (that each
have ONE dominant supertaster gene (S __))
have a child, the percentage chance of having a
___
S ___
S
___ ___
dominant supertaster (S __) is 75%.
s
When 2 Dominant Supertasters (that each have one
S
SS
Ss
dominant supertaster gene AND one recessive
supertaster gene (Ss)) have a child, the percentage
s
s
Ss
ss
s
s
ss
ss
chance of having a dominant supertaster (S __) is 75% and
the percentage of having a recessive supertaster is 25%.
When 2 Recessive Supertasters (that each have
2 recessive supertaster genes (ss)) have a child,
the percentage chance of having a dominant
s
ss
supertaster (S __) is 0% and the percentage chance
ss
of having a recessive supertaster (ss) is 100%.
This kit contains all of the materials necessary to determine if a person is a supertaster in
a scientifically sound way – utilizing a control paper to minimize sampling bias and error. The
purpose of the control is to provide a basis for comparison – the control paper strip has no
chemicals added, so it has “no taste.” The experience of “no taste” can thus be compared to
various taste experiences.
(A procedure for a group of 5 people participating in a supertaster experiment is included and it
can be adapted for 1 person or a class of 25 students.)
Copyright 2015, hBARSCI LLC
Supertaster Experiment
1. Assign each person a participant number, 1 through 5.
2. Out of the view of the five participants, (to avoid participants “expecting” various
tastes) setup the five testing sheets (example of testing sheet included) according to the
following grid:
Participant 1
Round 1
Control
Round 2
PTC
Round 3
Thiourea
Participant 2
PTC
Control
Participant 3
Thiourea
PTC
Sodium
Benzoate
Control
Participant 4
Sodium
Benzoate
Control
PTC
Control
Thiourea
PTC
Participant 5
Round 4
Sodium
Benzoate
Thiourea
Sodium
Benzoate
Thiourea
Sodium
Benzoate
3. Have each participant taste each strip by placing the strip on his/her tongue for a few
seconds – saliva will wet the paper and allow the flavor (or lack thereof) to be detected.
4. Have each participant write the taste of the strip in the box underneath the strip for each
round (none, salty, sweet, bitter, sour, or umami).
5. Gather results and use the chart below to determine what kind of “taster” each
participant is:
Phenotype
(Gene
Expression)
The person cannot
taste any difference
between the strips
The person can
only taste PTC
Label
Normal Taster
Genotype
(Genes in DNA)
____ ____ (No S
or s gene)
Standard
Supertaster
__ s
Copyright 2015, hBARSCI LLC
The person can taste
PTC and Thiourea,
but not Sodium
Benzoate
Recessive Supertaster
ss
The person can taste
PTC, Thiourea, and
Sodium Benzoate
Dominant
Supertaster
S ___
Participant _______________________
Round 1
Copyright 2015, hBARSCI LLC
Round 2
Round 3
Round 4