Download Cytochrome C Comparison Lab Purpose: To compare the

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. Draw the Practice Table and label 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
the common ancestor of all 8 organisms was living. This means that organism 8 is the same
number of years removed from organisms 1,2,3,4,5,6, and 7. Every junction represents a
time that the common ancestor of both branches was living.
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 (2) lines.
Differences: Tuna and Fly _______
In the example below there are 9 differences
C.
(Actual) Make a cladogram inside a circle (see other side) using data in Table 1.
a. First, complete data table using the information from white 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 hornworm branch to your
cladogram.
Hornworm
horse
penguin
snake
tuna
silkworm
yeast
wheat
26
28
24
28
5
42
38
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 possible reasons that the Cytochrome C data suggests that fungi, plants,
and animals are equally distantly related?
Trace into journal