Date
26
BIOCHEMICAL EVIDENCEFOR
EVOTUTION
If two organisms have similar DNA molecules, they have similar proteins. Simil:arProteins have
similar a'mino acid sequences(orders).Thus, il amino acid sequences are similar, DNA of the
organisms is similar.
Scientistsbelieve that similar DNA sequencesindicate a common origin. 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, gorillas, and horses.
In this investigation, you will
(a| count ind record differences in the sequence of amino acids in similar portions of
human, gorilla, and horse hemoglobin.
(bl count
r""oid the molecules oflach amino acid present in similar portions of human,
"tt[
gorilla, and horse hemoglobin.
(c) ise these data to show [ow biochemical evidencecan be used to support evolution.
Procedure
Part A. Amino Acid Sequence
Figure 25'1 on page 102 representsthe amino
acid sequence o{ corresponding portions of the
hemoglobin molecules of horses, goriilas, and
humans.
r Readthe amino acid sequencesfrom left to right
beginning at the upper left'hand comer of Figure
26-2. Compare the seguences of humans to the
sequencesof gorillas and horses. An example of a
sequencedifference between humans and gorillas
is shown in Figure 26-1.
o Record in Table 26-1 the total number of
differences in the sequencesof gorilla and human
amino acids. Then repeat this procedure for horse
and human, and for gorilla and horse.
His Pro I
Human:
Val
Gorilla:
Val
t
His Gly -lf
Horse:
Val
His Pro
J
TABLE25.1. NUMBEROF AMINO ACID
DIFFERENCES
SEQUENCE
ORCANISMS
N U M B E RO F D I F F E R E N C E S
Corilla
and human
Horse
and human
Corilla
and horse
Part B. Numbets of Amino Acids
. Count the number of each kind of amino acid in
human hemoglobin. Record the totals in the
proper column of. Table 26-2.
o Count each amino acid in the hemoglobin of
gorillas and horses. Record these in Table 26-2'
differencebetweenhumanand gorilla'
Thisis a sequence
differencebetweengorillaand horse'
l- rtris is a sequence
I
This is not a sequencedifference between human and horse.
FICURE26.1
r0l
FICURE26.2
Val
Val
Val
His
His
Glu
Leu Thr
Leu Thr
Leu ser
Human:
Gorilla:
Horse:
Gly
Cly
tup
Lys
Lys
Lys
val
Val
Val
Human:
Corilla:
Horse:
Human:
Corilla:
Horse:
Pro
Pro
Gly
clu
clu
clu
clu
Glu
clu
Lys ser
Lys ser
Lys Ala
Ala
Ala
Ala
val
Val
val
Thr Ala
Thr Ara
Leu Ara
Leu Try
Leu Try
Leu Trv
Asp val
Asp Val
Asp clu
Asp clu
Asp clu
clu Glu
Val
Val
Val
cly
cly
cly
cly
cly
Gly
clu
Glu
clu
Ala
Ala
Ala
Leu cly
Leu cly
Leu cly
Ar8
Arg
Arg
Leu Leu Val
Leu Leu Val
Leu Leu Val
Val
Val
Val
Tyr
Tyr
Tyr
Pro
Pro
Pro
Try
Try
Try
Thr
Thr
Thr
clu
clu
clu
Arg
Arg
Arg
phe
phe
phe
phe cru ser
phe cru ser
phe Asp ser
phe
phe
phe
Cly
Gly
Cly
Asp
Asp
Asp
Leu
Leu
Leu
Ser
Ser
Ser
Thr
Thr
Asp
Pro
Pro
Pro
Asp
Asp
Cly
Ala
Ala
Ala
Val
Val
Val
Met
Met
Met
Cly
Cly
Cly
Asp
ASp
Asp
pro
pro
pro
Val
Val
Val
Lys
Lys
Lys
Ala
Ala
Ala
His
His
His
Cly
Gly
cly
Lys
Lys
Lys
Lys
Lys
Lys
Val
Val
Val
Leu Cly
Leu cly
Leu His
Ala
Ala
ser
phe Ser
phe ser
phe crv
Lys
Lys
Lys
Asp Cly
Asp cly
cru crv
!
Leu
Leu
Val
!
Human:
Corilla:
Horse:
Human:
Gorilla:
Horse:
Ala
Ala
His
His
His
His
Leu Asp Asp Leu Lys
Leu Asp Asp Leu Lys
Leu Asp Asp Leu Lys
cly
Gly
cly
Thr
Thr
Thr
phe Ala
phe Ala
phe Ala
Thr
Thr
Ala
Leu ser
Leu ser
Leu ser
clu
clu
clu
Leu
Leu
Leu
His
His
His
Cys Asp
Cys Asp
Cys Asp
Lys
Lys
Lys
Val
Val
Val
Asp
Asp
Asp
Pro
Pro
Pro
Clu
Clu
Clu
Asp
Asp
Asp
Phe
Phe
Phe
Leu
Leu
Leu
Leu cly
Leu cly
Leu Gly
Asp Val
Asp Val
Asp Val
Leu Val
Leu Val
Leu Ala
Leu Ala
Leu Ala
Val Ala
His
His
Ar8
His
His
His
phe cly
phe cly
phe cly
Lys
Lys
Lys
Lys
Lys
Lys
Val
Val
val
Ata
Ata
Ala
Leu
Leu
Leu
His
His
His
cys Val
cys val
Leu Val
clu Phe Thr
Glu Phe Thr
Asp Phe Thr
Pro
Pro
Pro
Pro
Pro
clu
Val clu
Val clu
Leu Glu
Ala
Ala
Ala
Ala
Ala
ser
Tyr
Tyr
Tyr
Glu
clu
cru
Cly
Gly
Gly
Asp Ala
Asp Ala
Asp Ala
Leu Ala
Leu Ala
Leu Ala
His
His
His
Lys
Lys
Lys
Tyr
Tyr
Tyr
His
His
His
Val
Val
Val
Ala
Ala
Ala
Arg
Leu
Arg
Val
Val
Val
I
I
Date
Name
TABTE26-2.NUMBEROF EACHAMINO ACID
AMINO ACID
HUMAN
ABBREVIATION
Alanine
Ala
Arginine
Arg
Asparticacid
Asp
Cysteine
Cys
Clutamicacid
Glu
Clycine
clv
Histidine
His
Leucine
Leu
Lysine
Lys
Methionine
Met
Phenylalanine
Phe
Proline
Pro
Serine
Ser
Threonine
Thr
Tryptophan
Try
Tyrosine
Tyr
Valine
Val
CORILLA
HORSE
Analysis
1. Where is hemoglobin normally found?
2. Circle those words which corectly
apply to or describe hemoglobin: protein, carbohydrate,
composed of amino acids, chemical molecule, composed of DNA'
I
l.^
(--f
I
I
a. {af Which amino acid is most co@nimals?
{bl Which amino acid is next most ggmmon tn all three animals?
(ct Which amino acid is the least common in all three animals?
r03
I
6. Of the different types of amino acids found in hemoglobin,
(a) how many are present in the same exact number in humans and gorillas?
(b) in humans and horses?
(c) in gorillas and horses?
7. On the basis of your answer to question 6,
{a} how similar are the chemical makeups of human and gorilla hemoglobin?
{
I
t
(b) how similar are human and horse hemoglobin?
(c) how similar are gorilla and horse hemoglobin?
8 . Which two ani{nals_seem.toh"u.
@l
9. r ne sequenceot amlno acrclscorrespondsto the sequenceof base molecules in DNA. Are the
base
sequencesof DNA ,$$l;@r
in hlrman and go'illa, gorilla gn5|horse, or human and horse?
d
I
I
I
(
