TRAIT LAB
Instructions
Hypothesis#1: Our class will have more dominant/recessive (circle
one) traits because:__________________________________________
Hypothesis #2: I am very sensitive / not very sensitive (circle one) to
flavors and tastes on my tongue. I think that I will be able to taste ___
out of 3 taste tests today.
1.
In your row (Horizontal Row 1, 2, 3, or 4 ) survey each other on the following traits.
a. Widow’s Peak – a dominant trait – hair line comes to a point above the forehead
b. Can Roll Tongue – a dominant trait – tongue rolls to look like a hot dog bun
c. Free Ear Lobe – a dominant trait – ear lobe curves up to side of face instead of attaching
straight across
d. Righty or Lefty – being right handed is dominant over left handed. If you use both
hands, choose the hand you usually eat with.
e. Bent Little Finger – a dominant trait – hold your two pinky fingers side-by-side and see if
they line up straight or bend out at the top
f. Hitchhiker’s Thumb – a dominant trait – top joint of thumb bends back beyond joint
g. PTC Taster – a dominant trait – place a slip of PTC paper on your tongue. If you taste
“paper”, you are not a taster and have the recessive trait. If you get a strong taste, you are
a taster, which is dominant
h. Clasped Hands – a dominant trait – When you clasp your hands together (folding your
hands) if your left thumb is on top that is dominant. If your right thumb is on top, you
have the recessive trait
i. Thiourea – a dominant trait – place a slip of Thiourea on your tongue. If you taste
something strong and bitter, you are a taster (dominant). If you taste “paper”, you are not
a taster and are recessive.
j. Sodium Benzoate – a dominant trait. Follow the instructions for PTC and Thiourea. A
strong taste is dominant, a “paper” taste is recessive.
2.
Make a group data table: For each trait, record how many of you had the Dominant trait and how
many of you had the Recessive trait within your group. Record those numbers on your data sheet.
Your total is the number of people in your row. Then, use a calculator to determine the percent of
your results that had the dominant trait and the percent that had the recessive trait.
3.
Make a class data table: Next, send someone from your group to put your data on the board.
When all groups have posted their data, determine class totals of dominant, recessive, and
percents. The total would be the total number of students surveyed in the class today.
4.
Answer the following questions in your lab notebook in complete sentences.
a.
As a class, which traits did a majority of us have as the dominant trait?
b.
Which data results were the most surprising to you? Why?
c.
If we surveyed a larger group of individuals, such as the entire freshmen class, how do
you think our results might change? Give one or two examples.
d.
Could a person have all dominant traits and no recessive traits? Could they have all
recessive traits and no dominant traits? Explain.
e.
Closely examine the data for the three “taste papers”. If you are a non-taster for one
chemical, what does that mean for the other two tests? Make a data table comparing
these 3 results.
f.
Genetically speaking, the main PTC gene is located on chromosome # 7. Currently there
are two predominant, widely distributed forms of this gene. These forms are AVI and
PAV. Generally speaking, PAV probably is the dominant tasting allele and AVI is the
recessive non-tasting allele. Students with two PAV alleles will find PTC to taste very
bitter. Students with one PAV allele and one AVI allele will find a bitter taste, but not as
strong as someone with two PAV alleles. Students with two AVI alleles will be nontasters of PTC. Evolutionists have wondered if these genes play a role in our human
diets. For example, individuals with PAV alleles tend to avoid bitter tasting foods like
broccoli, cauliflower, and brussel sprouts. On the other hand, non-tasters with the AVI
alleles tend to eat a wide variety of green vegetables – perhaps because these foods are
not unpleasantly bitter to them. And, maybe being able to taste bitter components of
foods was a survival mechanism to protect individuals from ingesting poisonous
substances in the natural environment. Based upon this information, how would you
explain your genetics? What about the genetics of your immediate family
(mom/dad/siblings)?
g.
Is there a correlation between tasting (or not tasting) PTC and tasting the other two
substances? To respond, write a paragraph explaining and analyzing the data you
organized in part E and the information you gathered in part F.
5. Write a power conclusion about your findings. Compare your hypotheses back to your data results
as a class and as an individual (hypothesis #2). If you want to reference comparisons between small
groups and whole class to explain a main point, do so. Use specific data (numbers) to back up all
claims. Complete all 7 points in the power conclusion.