Download Cytochrome C Comparison Lab

Cytochrome C Comparison Lab
Purpose: To compare the relatedness between organisms by examining the amino acid sequence in the
protein Cytochrome C.
Background: Cytochrome C is a protein involved in using energy in the cell. Cytochrome C is found in
most, if not all, eukaryotes. Over time, random mutations in the DNA sequence occur. As a result the
amino acid sequence of Cytochrome C also changes. Cells without usable Cytochrome C are unlikely to
survive.
A. (Practice) Make a branching tree inside a circle or cladogram using your math.
a. First trace the example cladogram in your journal. Label the ends of the lines 1 through
8.
b. Construct a table and label the Practice Table with organisms 1-8.
c. Since the radius of the circle is the length equal to the greatest difference, choose a
number to represent the radius. The outside of the tree or circle represents time.
d. The radius represents the largest separation so the center of the circle is a past time
when all 8 had a common ancestor. This means that organism 8 is the same number of
years removed from organisms 1,2,3,4,5,6, and 7.
e. Continue to fill in the blanks on the practice table to explain the example cladogram.
B. (Method) Compare the amino acid sequence of Cytochrome C for Tuna and Fly. Note that some
of the amino acids are always the same in all species. These have been shaded light gray. Be
sure to study the entire molecule. Each protein sequence has 103- 112 amino acids; the
sequence extends onto two lines.
Differences: Tuna and Fly _______
In the example below there are 9 differences
----GDVAKGKKKTFVQKCAQCHTVENGGKHKVGPNLWGLFGRKT
GVPAG
C.
(Actual) Make a branching tree inside a circle, or cladogram using Table 1.
a. First, complete data table using the information from yellow sheet
b. Second, draw a new cladogram that shows the data from table 1. The radius of the
circle is the greatest difference in the amino acid sequence.
D. Questions
1. How many Cytochrome C amino acid sequence differences are there between
human/chimps and Rhesus monkeys?
2. Draw the position of the Rhesus monkey on your cladogram (show to teacher)
3. How many Cytochrome C amino acid sequence differences are there between chicken and
penguin?
4. Draw the position of the penguin on your cladogram. (Show to teacher)
5. Using the Cytochrome C sequence difference data to add a branch to your cladogram
Tomato
horse
penguin
snake
tuna
silkworm
yeast
wheat
26
28
24
28
5
42
38
Hornworm
Moth
6.
Explain why more closely related organisms have more similar Cytochrome C
7.
Other data, including other genes suggests that Fungi are more closely related to animals
than plants. What are some reasons that the Cytochrome C data suggests that fungi, plants,
and animals are equally distantly related?