Lab #
Amino Acid Sequence and Evolution
Date
I. Purpose: How do amino acid sequences provide evidence for evolution?
CA Standard: (8f) Students know how to use comparative embryology, DNA or protein sequence
comparisons, and other independent sources of data to create a branching diagram (cladogram) that
shows probable evolutionary relationships.
Background: Examine Table 1 which compares corresponding portions of hemoglobin molecules in
humans and five other vertebrate animals. Hemoglobin is a protein composed of several long chains
of amino acids and is the oxygen carrying molecule in red blood cells. The sequence shown is only a
portion of a chain made up of 146 amino acids. The numbers in Table 1 indicate the position of a
particular amino acid in the chain.
Another commonly studied protein is cytochrome c. This protein consists of 104 amino acids and
is located in the mitochondria of cells. There it functions as a respiratory enzyme. Figure 2 uses
human cytochrome c as a standard and reveals the amino acid differences between humans and a
number of other organisms.
II. Materials:
hemoglobin sequence
cytochrome c data
III. Procedure:
Part A: Comparing Amino Acid Sequences
1. Using Table 1, circle the name of each amino acid in the chimpanzee hemoglobin that is different
from that in human hemoglobin. If there are no differences, then do not circle the amino acid.
2. For the remaining organisms circle the names of the amino acids that are different to those in
human hemoglobin. Note: Always be sure that you compare the amino acid sequence of each
organism with that of the human and not the organism on the line above.
Part B: Inferring Evolutionary Relationships from Differences in Amino Acid Sequences
1. Fill in the bar graph that is patterned after Table 3 (the bars will go sideways). This will show the
amino acid differences among several organisms.
2. Make a bar graph that is patterned after Table 4 (the bars will go sideways). The cytochrome c of a
fruit fly is used as a standard in comparing amino acid differences among several organisms
IV. Data/Observations
Table 1
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
THR
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
THR
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
THR
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
GLN
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
ALA
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
LYS
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
Human
Chimpanzee
Gorilla
Rhesus monkey
Horse
ASN
PHE
ARG
LEU
LEU
GLY
ASN
VAL
LEU
VAL
CYS
VAL
LEU
ALA
HIS
ASN
PHE
ARG
LEU
LEU
GLY
ASN
VAL
LEU
VAL
CYS
VAL
LEU
ALA
HIS
ASN
PHE
LYS
LEU
LEU
GLY
ASN
VAL
LEU
VAL
CYS
VAL
LEU
ALA
HIS
ASN
PHE
LYS
LEU
LEU
GLY
ASN
VAL
LEU
VAL
CYS
VAL
LEU
ALA
HIS
ASN
PHE
ARG
LEU
LEU
GLY
ASN
VAL
LEU
ALA
LEU
VAL
VAL
ALA
ARG
Kangaroo
ASN
PHE
LYS
LEU
LEU
GLY
ASN
ILE
ILE
VAL
ILE
CYS
LEU
ALA
GLU
Human
Chimpanzee
Gorilla
Rhesus monkey
Horse
Kangaroo
Human hemoglobin is being used as the standard for comparison.
Data Table 2 (Summarize the information in Table 1)
Organism
Human and
chimpanzee
Human and
gorilla
Human and
rhesus monkey
Human and
horse
Human and
kangaroo
Number of Amino
Acid Differences
Positions in Which They Vary
(Write the amino acid # where there is a difference)
104,
V. Calculations/Results
Table 3
Species Pairings
Number of
Differences
0
29
12
12
14
48
1
27
15
21
43
Human – chimpanzee
Human – fruit fly
Human – horse
Human – pigeon
Human – rattlesnake
Human – red bread mold
Human – rhesus monkey
Human – screwworm fly
Human – snapping turtle
Human – tuna
Human – wheat
Graph 1
Number of Differences
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Species Pairings
Human – chimpanzee ------------Human – fruit fly -----------------Human – horse --------------------Human – pigeon ------------------Human – rattlesnake --------------Human – red bread mold ---------Human – rhesus monkey ---------Human – screwworm fly ---------Human – snapping turtle ---------Human – tuna ----------------------Human – wheat --------------------
Table 4
Species Pairings
Fruit fly – dogfish shark
Fruit fly – pigeon
Fruit fly – screwworm fly
Fruit fly –silkworm moth
Fruit fly –tobacco hornworm moth
Fruit fly – wheat
Graph 2
Number of
Differences
26
25
2
15
14
47
Number of Differences
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Species Pairings
Fruit fly – dogfish shark ------------Fruit fly – pigeon --------------------Fruit fly – screwworm fly ----------Fruit fly –silkworm moth -----------Fruit fly –tobacco hornworm moth
Fruit fly – wheat ----------------------
VI. Questions (Re-state the questions and answer in a complete sentence.)
1. What is hemoglobin? What is its function? How many amino acids make up 1 chain of
hemoglobin? (Read the Background.)
Use Table 2 to answer question 2.
2. On the basis of hemoglobin similarity, what organisms appear to resemble humans most closely and
which seem to be least closely related to humans? Explain your answer.
3. What organelle is cytochrome c found in? How many amino acids make 1 protein of cytochrome c?
What is the function of the cytochrome c protein? (Read the Background.)
Use Table 3 answer questions 4 & 5.
4. On the basis of differences in their cytochrome c, which organisms appear to be most closely
related to humans? Which organisms are the least closely related to humans?
5. Name the pair of organisms that appear to be equally related to humans on the basis of cytochrome
c similarity.
6. If the amino acid sequences in the proteins of two organisms are similar, then why will their DNA
also be similar?
VII. Conclusion:
How do amino acid sequences provide evidence for evolution?