Enduring Understanding
Changes occur in species resulting in biodiversity.
Biology Student
EQ: Why do horses have hooves?
Broad Brush Knowledge
evidence of evolution
Amino Acid
Sequencing
Concepts Important to Know and Understand
Evolution, Patterns, Constancy & Change
Targeted Skills
sequencing, analyzing, comparing
Core Objectives
Identify evidence of change in species using fossils, DNA sequences,
anatomical similarities, physiological similarities, and embryology.
PURPOSE: To analyze amino acid sequences as a guide for relationships and common ancestry.
Scientists can examine the amino acid sequences of particular protein molecules found in vertebrates to
determine the degree of similarity between vertebrate species. Even organisms that appear to have few
physical similarities may have similar sequences of amino acids in their proteins and be closely related
through evolution. Scientists believe that the greater the similarity in the amino acid sequences of two
organisms, the more closely related they are in an evolutionary sense.
Part A: Cytochrome-c is a protein found in the mitochondria that is used in cellular respiration. This protein
consists of a chain of 104 amino acids. The chart below shows the amino acid sequence of nine vertebrates.
The letters identify the name of the amino acid.
Animal
Horse
Chicken
Tuna
Frog
Human
Shark
Turtle
Monkey
Rabbit
A
B
C
D
E
F
G
Amino Acid Sequences in Cytochrome-c
H
I
J
K
L
M
N O
P
Q
R
S
T
U
V
gln
gln
gln
gln
gln
gln
gln
gln
gln
pro
glu
glu
ala
pro
gln
glu
pro
val
phe
phe
phe
phe
tyr
phe
phe
tyr
phe
thr
ser
ser
ser
ser
ser
ser
ser
ser
thr
thr
thr
thr
thr
thr
thr
thr
thr
ala
asp
asp
asp
ala
asp
glu
ala
asp
lys
lys
lys
lys
lys
lys
lys
lys
lys
asn
asn
ser
asn
asn
ser
asn
asn
asn
glu
glu
glu
glu
glu
ile
glu
glu
glu
lys
lys
ser
ser
lys
lys
asp
lys
lys
ala
ala
ala
ala
ala
thr
ala
ala
ala
thr
thr
thr
cys
thr
ala
thr
thr
thr
asn
ser
ser
ser
asn
ala
ser
asn
asn
glu
lys
-lys
glu
ser
lys
glu
glu
lys
lys
lys
lys
lys
lys
lys
lys
lys
thr
thr
val
thr
ile
thr
thr
thr
thr
lys
gly
asn
gly
gly
gln
gly
gly
gly
glu
glu
asn
glu
glu
gln
glu
glu
glu
glu
asp
asp
asp
asp
glu
asp
asp
asp
thr
thr
thr
thr
thr
thr
thr
thr
thr
leu
leu
leu
leu
leu
leu
leu
leu
leu
met
met
met
met
met
arg
met
met
met
DATA
Compare the amino acid sequence
of human cytochrome-c with that of
the other eight vertebrates. For
each vertebrate, count the number of
amino acids that differ from those in
the human and write the number in
the chart to the right.
TABLE 1
Number of Amino Acid Differences
from Human Cytochrome-c
Number
Species
Differences
Human
0
Horse
Chicken
Tuna
Frog
Shark
Turtle
Monkey
Rabbit
Amino Acid Sequencing - Student (Revised June 1, 2004)
(printed 2/13/2016) p. 1
DATA ANALYSIS
1. Based on the data, list the order
in which these vertebrates are
related to humans. Place the
vertebrates more similar to
humans in sequence at from the
top.
TABLE 2
Similarity Ranking
Animal
AA Difference
Human
0
2. Using the amino acid differences, which organism is most closely related to humans? ____________
3. Using the amino acid differences, which organism is least closely related to humans? ____________
4. A cladogram is a tree-like diagram showing evolutionary relationships. Use the data from Table 2 and
fill in the cladogram to show the relationship of these animals compared to the human. Label the
location on the cladogram where you would place the common ancestor to all of these animals.
0
5
10
15
Number of Amino Acid Differences
5. In the table you completed above, the number listed for the chicken and horse as compared to the
human differs by only one. Compare the differences in amino acid sequences between the horse and
the chicken. The difference is ____ . Considering both sets of data, can you conclude from this that
the horse and the chicken are closely related? _______ Why or why not? _____________________
________________________________________________________________________________
CONCLUSION:
Summarize the concept of amino acid comparisons as they would indicate the possibility/closeness of a
common ancestor.
________________________________________________________________________________
________________________________________________________________________________
Amino Acid Sequencing - Student (Revised June 1, 2004)
(printed 2/13/2016) p. 2