Name: ______Date: ______

Determining Our Traits

Objectives:

a)  to study the inheritance of some human traits

b)  to determine the frequency of selected traits in a given population

c)  to see the extent of genetic variability

Procedure:

1.  For each row in the data table on the next page, determine which trait you have (your PHENOTYPE). Use your laminated trait sheets to help you.

2.  From this, determine your GENOTYPE for each trait and record it in the same data table. (Note: We will use only a single symbol to indicate dominance since we do not know whether we are homozygous or heterozygous for the trait).

3.  Get into groups of 4-6 and together complete the chart on this page. In the box for each trait, write the initials for all the group members that have that trait. (For example, if three of you are dominant, or E, for ear lobes, then put those three sets of initials in the box for “E”). Each group member should complete the chart on his/her own paper.

Group Member Names: ______, ______, ______, ______, ______, ______

Trait / Your Phenotype / Your Genotype / Dominant # in Class / Recessive # in Class / Ratio of Dominant to Recessive / Frequency (%) of your trait in class
Ear Lobes
E = free
e = attached
Widow’s Peak D = have
d = don’t have
Tongue Rolling R = can do
r = can’t do
Bent Little Finger
B = have
b =don’t have
PTC Tasting
T = can taste
t = can’t taste
Mid digital hair M = have
m = don’t have

Procedure (Continued): When you are finished, begin answering the discussion questions below. When everyone is done we will fill in the rest of the data table above as a class and discuss the results.

Discussion Questions:

1.  How many people in your group had at least two traits in common with you? Did anyone have exactly the same traits as you?

2.  Would two people who had the same genotype for all the traits in this activity look alike? Why or why not?

3.  Why are there always two letter choices (capital and lowercase) for each trait?

4.  Approximately 75% of people in the US are PTC tasters (T). How does this compare to the ratios we obtained? Why might our ratios not match the national average?

5.  Is it possible for two people with free ear lobes (E) have a baby with attached ear lobes (e)?

6.  Is it possible for a recessive trait to be more frequent in a population than a dominant one? Why or why not?

Adapted by Ms. A. Cook from activities by Ms. Judy Jones, ECHHS and Ms. Becky Smith, OHS March 2012