BIOL 170 Exploring Biology
Heredity: Human Genetic Traits Activity
11/06
Part 1: First class period and homework
The following is a list of human genetic characteristics (traits), which follow traditional
Mendelian inheritance (one gene per trait).
Task 1: Determine your phenotype for each trait listed.
Trait
dominant
1. Freckles
freckles (F)
2. Earlobes
free (E)
3. Cheek dimples
dimples (D)
4. Hand clasp
left thumb top (I)
5. Hairline
widow’s peak (W)
6. Eye Color
brown/green/hazel (B)
7. Handedness
right-handed (R)
8. Cleft chin
cleft (C)
9. Tongue rolling
tongue roller (T)
recessive
no freckles (f)
attached (e)
no dimples (d)
right thumb top (i)
no peak (w)
blue/gray (b)
left-handed (r)
round (c)
non-tongue roller (t)
Task 2: Determine, as close as possible, your genotype. To determine your genotype
you should collect as much phenotype information about your parents and siblings as
available and use that information to determine your genotype. Use the coding (letter)
given for each trait, indicate dominant or recessive alleles in writing your genotype.
Prepare a data table with your family’s phenotype data of these traits for use at the
beginning of the second class period.
Part 2: Second class period
Task 2 continued: Finish determining your phenotype from the phenotype data of your
parents and siblings. Your instructor can help you here.
Task 3: We will construct a class data table of your genotypes for the above list.
Your instructor will assign a genotype from the class data table. Using your genotype for
the assigned trait:
Task 4: Let us explore what happens to the genotype of the selected trait over five
generations of sexual reproduction: Does passing on half your genes increase diversity?
Follow these directions:
1. Find a classmate (disregarding any physiological impossibility) and produce a
Punnett square of your potential offspring for the genotype assigned by your
instructor. Start with your genotype for the assigned trait and your classmate’s
genotype.
2. Randomly select (indicate this by circling the genotype in the Punnett Square) one
genotype for your offspring from those determined in step #1. This “child” will
now “mate” with a second classmate and determine using a Punnett square their
potential offspring.
3. Repeat steps 2 with different classmates until you are five generations from your
original you.
Next class period: You should come with your five Punnett Square generations done.
We will create a second class data table of the possible genotypes of everyone’s fifth
generation. For the class data table recorded in task 3, we can get the genotype for all
of you “parents.”
Task 5: Prepare a report (worth up to 15 points) and include:
a. Your family phenotypes data table including your genotype data too.
b. The Punnett square for each generation, first through fifth generation for
the trait you were assigned.
c. A table showing the comparison of possible genotypes between the class’s
first generation (the “parents”) and the class’s fifth generation of the trait
you were assigned.
d. Answer the question: Did passing on half our genes increase the diversity
of the classes gene pool? Explain the evidence for your answer.