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Anthr 105
Biological Anthropology Lab
Dr. Bolter
Exercise
Human Genetics Survey
A person's phenotype results from the interaction of the genotype and the
environment. However, there are a small number of human traits which do
not appear to be affected by the external environment and which occur in a
significantly high frequency.
Problem
The following traits can be used to illustrate some of the basic principles of
genetics. They are described below along with their mode of inheritance.
Your task:
(a). Record your phenotype and possible genotypes for each trait at the end
of each description.
(b). Interview 10 subjects for the traits listed and record the information,
and record on the attached interview sheet. (Your team-mates count as
interviewees.)
(c). Record your team’s results onto the master sheet in the classroom.
When the class master chart is completed, copy the data onto the attached
mini-master sheet.
(d). Compare your team’s sample to the compiled class pool. In what way
do your sample population results differ from the total population sample of
the class?
Answer:
Human Genetics Page 1 of 5
Modified from Phil Stein, lab manual for Physical Anthropology
by Stein, P. and Rowe, B.
Anthr 105
Biological Anthropology Lab
Dr. Bolter
1. Tongue rolling This trait involves the ability to roll your tongue
longitudinally into a U–shape. Many people are incapable of performing
this feat. Although in a few cases practice is necessary for those with the
genetic potential to roll their tongues, those who are “nonrollers” are never
able to do so. This ability is inherited as a dominant; those who cannot roll
their tongues are homozygous recessive.
My phenotype:
My genotype:
2. Tongue folding This trait involves the ability to turn the tip of your
tongue back upon the main body of the tongue without using the teeth in any
way. Like tongue rolling, tongue folding may require some practice among
those who have the potential to perform this act. Tongue folding is inherited
as a recessive. Therefore, those who can fold their tongues are homozygous
recessive. By the way, tongue rolling and tongue folding are inherited
independently of one another.
My phenotype:
My genotype:
3. Earlobes Individuals with attached earlobes are characterized by the
attachment of the lower part of the ear directly onto the head. Although
there may be variations in the shape of the lower part of the ear, a free–
hanging lobe is absent. The attached earlobe, or lack of a free–hanging lobe,
is inherited as a recessive.
My phenotype:
My genotype:
4. Darwin tubercle The Darwin tubercle is a projection on the helix of the
ear resulting from a thickening of the cartilage. The actual size of the
tubercle varies. The tubercle is inherited as a dominant, but its expression is
variable. Some individuals with the dominant allele may show the tubercle
on only one ear and a minority of individuals may not show it at all.
Human Genetics Page 2 of 5
Modified from Phil Stein, lab manual for Physical Anthropology
by Stein, P. and Rowe, B.
Anthr 105
Biological Anthropology Lab
Dr. Bolter
My phenotype:
My genotype:
5. Earwax Earwax, or cerumen, occurs in two basic forms. The dry form
is gray and brittle while the wet form is brown and sticky. The dry form is
inherited as a recessive.
My phenotype:
My genotype:
6. Hitchhiker's thumb Put your hand in a hitchhiker's position. Try to
bend your thumb at the middle joint at a sharp angle (50 degrees or more).
If you can, you have hitchhiker's thumb, or distal hyperextensibility. This
ability is inherited as a recessive.
My phenotype:
My genotype:
7. PTC tasting PTC, or phenylthiocarbamide, is a human–made chemical.
This human-made chemical mimics one found in certain foods, like brussel
sprouts and kale. While the majority of people find PTC to have a bitter
taste, many find this substance tasteless. If you can taste this chemical, you
probably don’t like brussel sprouts because they taste bitter. PTC tasting is
inherited as dominant.
My phenotype:
My genotype:
Human Genetics Page 3 of 5
Modified from Phil Stein, lab manual for Physical Anthropology
by Stein, P. and Rowe, B.