Inherited Traits Survey
Name _____________________________
Date __________________ Period _____
In this exercise you will examine 13 easily observed traits in order to look at human
variation. Your job is to determine whether or not you possess each of these traits and
then determine your probable genotype (dominant homozygote, heterozygote, recessive
homozygote). Collecting these data from your classmates, you will then determine gene,
genotype and phenotype frequencies for your lab section, and then for the entire class.
Even in a group as small as your lab section you should see a great deal of variation between
individuals. Work on this project with a partner.
Instructions:
1) Fill out Data Sheet #1 with the help of your partner, from your observations of each
other.
2) Combine the information from the entire group, including you and your partner, and
fill in Data Sheet #2 (we’ll do this together).
3) Calculate the % of the total of dominant and recessive phenotypes for each trait in
your lab section, and fill in Data Sheet #3.
4) Show all work, and attach worksheets to the back.
Trait 1: Widow’s Peak
In some people the hairline drops downward and forms a distinct point in the
center of the forehead. It results from the action of a certain dominant
gene
(W).
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Trait 2: Attached Earlobes
Most people have earlobes that hang free, but when a person is homozygous
for the recessive gene (e) the earlobes are attached directly to the side of
the head.
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Trait 3: Darwin’s Point
The Darwin’s point is a small projection of the cartilage on the helix of the
ear. The presence of the point is dominant (D) and the absence is recessive
(d).
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Trait 4: Hair Whorl Pattern
Hair whorl pattern refers to the direction that the hair
naturally falls from the “part” on top of your head. A clockwise
pattern is dominant (H) and a counterclockwise pattern is
recessive (h).
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Trait 5: Pigmented Iris
A person homozygous for recessive gene (b) has no pigment in the iris, which makes the
eyes appear blue. Other genes determine the amount of pigments that give differently
colored eyes. Consider blue or gray eyes (bb), brown eyes (BB) and green, hazel, etc (Bb).
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Trait 6: Tongue Rolling
The ability to roll your tongue in a U-shape comes from a dominant gene
(R).
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Trait 7: Tongue Folding
The ability to turn the tip of the tongue back upon the body of the tongue
is inherited as a recessive trait (f). Tongue rolling and tongue folding are
inherited separately.
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Trait 8: Hitchhiker’s Thumb
Some people with recessive gene (t) are able to bend their thumb joint to as much as a 45°
angle.
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Trait 9: Bent Little Finger
A dominant gene (B) causes the last joint of the little finger to bend inward toward the
fourth finger. Lay both hands flat on the table, relax the muscles, and note whether you
have a bent or straight little finger.
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Trait 10: Long Palmar Muscle
Clench your fist tightly and flex your hand. If you see or feel 3 tendons, you have the long
palmar muscle from recessive gene (l). If there are only 2 tendons, you do not have this
muscle.
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Trait 11: Mid-Digital Hair
Observe the middle segment of all your fingers and note the presence or absence of hair
on this segment. The presence of hair is dominant (M) and the absence is recessive (m).
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Trait 12: Index Finger Shorter than Ring Finger
Hold your fingers together and place your hand on a sheet of paper so that the fingers are
at right angles to a horizontal line on the paper. Move your hand slowly up until the tip of
your ring finger touches the line. If your index finger does not touch the line, it is shorter
than your ring finger. The recessive gene for this trait is (s).
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Trait 13: Interlocking Fingers and Thumbs
Without looking at your hands, fold your hands and interlock your
fingers. Now look: if the left thumb is over the right thumb, this is the
dominant position (I). If the right thumb is over the left thumb, this is
the recessive position (i).
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RESULTS
TRAIT
GENE
Widow’s Peak
Attached Earlobes
Darwin’s Point
Clockwise Hair Whorl
Pigmented Iris
Tongue Rolling
Tongue Folding
Hitchhiker’s Thumb
Bent Little Finger
Long Palmar Muscle
Mid-digital Hair
Index Finger Shorter than Ring Finger
Interlocking Fingers and Thumb
ME
YOU
W
e
D
H
b (blue)
R
f
T
B
L
M
s
I
Data Table 1
TRAIT
Widow’s Peak
Attached Earlobes
Darwin’s Point
Clockwise Hair Whorl
Pigmented Iris
Tongue Rolling
Tongue Folding
Hitchhiker’s Thumb
Bent Little Finger
Long Palmar Muscle
Mid-digital Hair
Index Finger Shorter than Ring Finger
Interlocking Fingers and Thumb
Data Table 2
Number
Dominant
%Dominant
Number %Recessive
Recessive
Analysis:
1. Who is Gregor Mendel and why do we call this type of genetics Mendelian
Genetics?
2. Define the difference between dominant and recessive traits.
3. What is a genotype? What is a phenotype?
4. Do you think anyone in your class has all the same genetic traits that you have?
Explain your answer.