Download Evolution - Amino Acid wksht

NAME ________________________________________ DATE_________________ PERIOD_______
Amino Acid Sequencing
Proteins are made of amino acids. DNA determines what sequence these amino acids must be in to build the protein. Scientists
can examine the amino acid sequence of particular protein molecules found in vertebrates to determine the degree of similarity
between 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
(DNA 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
gln
pro
phe
thr
thr
ala
lys
asn
lys
gln
glu
phe
ser
thr
asp
lys
asn
lys
thr
gln
glu
phe
ser
thr
asp
lys
ser
lys
val
gln
ala
phe
ser
thr
asp
lys
asn
lys
thr
gln
pro
tyr
ser
thr
ala
lys
asn
lys
gln
gln
phe
ser
thr
asp
lys
ser
lys
gln
glu
phe
ser
thr
glu
lys
asn
lys
gln
pro
tyr
ser
thr
ala
lys
asn
lys
gln
val
phe
ser
thr
asp
lys
asn
lys
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.
P
Q
R
S
T
U
V
glu
glu
thr
leu
met
glu
lys
ala
thr
asn
glu
gly
glu
asp
thr
leu
met
glu
lys
ala
thr
ser
lys
asn
asn
asp
thr
leu
met
glu
ser
ala
thr
ser
--
gly
glu
asp
thr
leu
met
glu
ser
ala
cys
ser
lys
ile
gly
glu
asp
thr
leu
met
glu
lys
ala
thr
asn
glu
thr
gln
gln
glu
thr
leu
arg
ile
lys
thr
ala
ala
ser
thr
gly
glu
asp
thr
leu
met
glu
asp
ala
thr
ser
lys
thr
gly
glu
asp
thr
leu
met
glu
lys
ala
thr
asn
glu
thr
gly
glu
asp
thr
leu
met
glu
lys
ala
thr
asn
glu
thr
TABLE 1
lys
Number of Amino Acid Differences
from Human Cytochrome-c
Number
Species
Differences
Human
Horse
Chicken
Tuna
Frog
Shark
Turtle
Monkey
Rabbit
0
NAME ________________________________________ DATE_________________ PERIOD_______
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
5.
Number of Amino Acid Differences
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.