Name: _______________________________________________ Date: ________________ Period: ______
Biology: Biochemical Evidence for Evolution
Background Information: If two organisms have similar DNA molecules, they must have similar amino
acids and thus similar proteins. Therefore, DNA comparisons can be made by examining the sequences of
amino acids within a protein.
Scientists have long believed that similar DNA sequences indicate a common origin and ancestor. The more
similar the DNA of two living organisms, the more closely related they may be to one another. Hemoglobin,
a protein in red blood cells, has been studied. Scientists know the specific amino acids and their
arrangements in hemoglobin molecules of humans, gorilla, and horses.
In this investigation, you will
a. count and record the molecules of each amino acid present in similar portions of humans, gorilla, and
horse hemoglobin.
b. Count and record differences in the sequence of amino acids in similar portions of human, gorilla,
and horse hemoglobin.
c. Use this data to show how biochemical evidence can be used to support evolution.
Procedure
Part A: Amino Acid Sequence
1) Read the amino acid sequences from left to right beginning at the upper left hand corner of figure 391. Compare the sequences of humans to the sequences of gorillas and horses. An example of a
sequence difference between humans and horses is shown in figure 39-1.
2) Record in Table 39-1 the total number of differences in the sequences of gorilla and human amino
acids. Then repeat this for horse and human, and for gorilla and horse.
Table 39-1. Number of Amino Acid Sequence Differences
Organisms
Number of Differences
Gorilla and Human
Horse and Human
Gorilla and Horse
Using the information you collected, graph the differences between the three organisms below. Be sure to
title your graph and label both axes.
Part B: Numbers of Amino Acids
1) Figure 39-1 represents the amino acid sequence of corresponding portions of the hemoglobin
molecules or horses, gorillas, and humans.
2) Count the molecules of each kind of amino acid in human’s hemoglobin. Record the totals in the
proper column of table 39-2.
Figure 39-1
Human: VAL
Gorilla: VAL
Horse: VAL
HIS
HIS
GLU
LEU
LEU
LEU
THR
THR
SER
Human: GLY
Gorilla: GLY
Horse: ASP
LYS
VAL
ASP
VAL
ASP
GLU
VAL
GLY
GLY
GLU
ALA
LEU
GLY
ARG
LYS
VAL
ASP
VAL
ASP
GLU
VAL
GLY
GLY
GLU
ALA
LEU
GLY
ARG
LYS
VAL
ASP
GLU
GLU
GLU
VAL
GLY
GLY
GLU
ALA
LEU
GLY
ARG
TYR
TYR
TYR
GLU
GLU
GLU
Human: LYS
Gorilla: LYS
Horse: LYS
ALA
ALA
ALA
HIS
HIS
HIS
GLY
GLY
GLY
LYS
LYS
LYS
LYS
LYS
LYS
VAL
VAL
VAL
LEU
LEU
LEU
GLY
GLY
HIS
ALA
ALA
SER
Human: ALA
Gorilla: ALA
Horse: HIS
HIS
HIS
HIS
LEU
LEU
LEU
ASP
ASP
ASP
ASP
ASP
ASP
LEU
LEU
LEU
LYS
LYS
LYS
GLY
GLY
GLY
THR
THR
THR
PHE
PHE
PHE
Human: LEU
Gorilla: LEU
Horse: LEU
HIS
HIS
HIS
CYS
CYS
CYS
ASP
ASP
ASP
LYS
LYS
LYS
LEU
LEU
LEU
HIS
HIS
HIS
Human: LEU
Gorilla: LEU
Horse: LEU
GLY
GLY
GLY
ASP
ASP
ASP
VAL
VAL
VAL
LEU
LEU
LEU
VAL
VAL
ALA
CYS
CYS
LEU
VAL
VAL
VAL
LEU
LEU
VAL
ALA
ALA
ALA
Human: GLU
Gorilla: GLU
Horse: ASP
PHE
PHE
PHE
THR
THR
THR
PRO
PRO
PRO
PRO
PRO
GLU
VAL
VAL
LEU
GLU
GLU
GLU
ALA
ALA
ALA
ALA
ALA
SER
TYR
TYR
TYR
ASP
ASP
ASP
ALA
ALA
ALA
LEU
LEU
LEU
ALA
ALA
ALA
VAL
VAL
VAL
ALA
ALA
ALA
GLU
GLU
GLU
VAL
VAL
VAL
LEU
LEU
LEU
THR PRO ASP
THR PRO ASP
ASP PRO GLY
THR
THR
THR
ALA
ALA
ALA
ASP
ASP
ASP
ALA
ALA
ALA
TRY
TRY
TRY
SER
SER
ALA
Human: GLY
Gorilla: GLY
Horse: GLY
SER
SER
SER
PRO
PRO
PRO
LYS
LYS
LYS
LEU
LEU
LEU
VAL
VAL
VAL
VAL
VAL
VAL
GLU
GLU
GLU
Human: LEU
Gorilla: LEU
Horse: LEU
Human: GLY
Gorilla: GLY
Horse: GLY
VAL
VAL
VAL
PRO
PRO
GLY
VAL
VAL
VAL
ASP
ASP
ASP
HIS
HIS
HIS
ARG
ARG
ARG
MET
MET
MET
PRO
PRO
PRO
LYS
LYS
LYS
THR
THR
LEU
PHE
PHE
PHE
PHE
PHE
PHE
GLY
GLY
GLY
ASP
ASP
ASP
PHE
PHE
PHE
SER
SER
GLY
ALA
ALA
ALA
GLU
GLU
GLU
THR
THR
ALA
ASP
ASP
ASP
HIS
HIS
ARG
ALA
ALA
ALA
GLU
GLU
ASP
PRO
PRO
PRO
GLU
GLU
GLU
LYS
LYS
LYS
TYR
TYR
TYR
HIS
HIS
HIS
SER
SER
SER
LYS
LYS
LYS
TRY
TRY
TRY
PHE
PHE
PHE
VAL
VAL
VAL
ASP
ASP
GLU
GLY
GLY
GLY
LEU
LEU
VAL
LEU
LEU
LEU
SER
SER
SER
GLU
GLU
GLU
PHE
PHE
PHE
HIS
HIS
HIS
LEU
LEU
LEU
ARG
LEU
ARG
LEU
LEU
LEU
PHE
PHE
PHE
GLY
GLY
GLY
LYS
LYS
LYS
VAL
VAL
VAL
VAL
VAL
VAL
ALA
ALA
ALA
Table 39-2. Number of Each Amino Acid
Amino Acid
Abbreviation
Alanine
Ala
Arginine
Arg
Aspartic acid
Asp
Cysteine
Cys
Glutamic acid
Glu
Glycine
Gly
Histidine
His
Leucine
Leu
Lysine
Lys
Methionine
Met
Phenylalanine
Phe
Proline
Pro
Serine
Ser
Threonine
Thr
Tryptophan
Try
Tyrosine
Tyr
Valine
Val
Human
Gorilla
Horse
Data Analysis:
1) Of the 17 different types of amino acids found in hemoglobin,
a. How many are present in the same number in humans and gorillas? ________________________
b. In humans and horse? ____________________________________________________________
c. In gorillas and horses? ____________________________________________________________
2) Neatly, list all the possible DNA codes for the amino acid Leucine.
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3) Which amino acid would be created from the DNA segment TTA? ___________________________
Be sure to answer the following questions using your best writing skills.
4) Which two animals seem to have more similar hemoglobin? Explain your reasoning.
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5) What if the DNA had a mutation and the code was changed to TTG (instead of TTA). How would
this affect the overall amino acid and protein?
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6) The sequence of amino acids is determined by the sequence of nitrogen bases in DNA. What can we
conclude about the DNA sequence of these three animals?
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7) In your own words, describe what it means when different organisms such as a gorilla and human
have similar amino acids in the protein hemoglobin.
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