biochemical evidence for evolution -...
TRANSCRIPT
Name Period Date
Biochemical Evidence for Evolution
If two organisms have similar DNA molecules, they have similar proteins. Similar proteins have similaramino acid sequences (orders). Thus, if amino acid sequences are similar, DNA of the organisms is similar.
Scientists believe that similar DNA sequences indicate a common origin. The more similar the DNA of twoliving 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 theirarrangements in hemoglobin molecules of humans, gorillas, and horses.
In this investigation, you will(a) count and record differences in the sequence of amino acids in similar portions of human,
gorilla, and horse hemoglobin.count and record the molecules of each amino acid present in similar portions of human,gorilla, and horse hemoglobin.use these data to show how biochemical evidence can be used to support evolution.
(b)
(c)
ProcedurePart A. AminoAcid Sequence
Figure 2 on the next page represents theamino acid sequence of corresponding portions ofthe hemoglobin molecules of horses, gorillas, andhumans.
* Read the amino acid sequences from left to rightbeginning at the upper left-hand comer of Figure2. Compare the sequences of humans to thesequences of gorillas and horses. An example of asequence difference between humans and gorillasis shown in Figure 1.
*Record in Table 1 the total number of differencesin the sequences of gorilla and human aminoacids. Then repeat this procedure for horse andhuman, and for gorilla and horse.
FIGURE1
Human: Pro
Gorilla: Gly
Horse: Pro
Part B. Numbers of Amino Acids*Count the number of each kind of amino acid inhuman hemoglobin. Record the totals in the propercolumn of Table 2.
*Count each amino acid in the hemoglobin ofgorillas and horses. Record these in Table 2.
This is a sequence difference between human and gorilla.
This is a sequence difference between gorilla and horse.
This is not a sequence difference between human and horse.
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Val His
Val His
Val His
TABLE 1.NUMBER OF AMINO ACIDSEQUENCE DIFFERENCES
ORGANISMS NUMBER OF DIFFERENCES
Gorilla
and human
Horse
and human
Gorilla
and horse
Human:Gorilla:Horse:
Human:Gorilla:
Horse:
Human:Gorilla:Horse:
Human:Gorilla:Horse:
Human:Gorilla:Horse:
Human:Gorilla:Horse:
Human:Gorilla:Horse:
Human:Gorilla:
Horse:
GlyGlyAsp
LeuLeuLeu
GlyGlyGly
LysLysLys
AlaAlaHis
LeuLeuLeu
LeuLeuLeu
GluGluAsp
LysLysLys
LeuLeuLeu
AspAspAsp
AlaAlaAla
HisHisHis
HisHisHis
GlyGlyGly
PhePhePhe
ValValVal
ValValVal
LeuLeuLeu
HisHisHis
LeuLeuLeu
CysCysCys
AspAspAsp
ThrThrThr
AspAspAsp
ValValVal
SerSerSe'r
GlyGlyGly
AspAspAsp
AspAspAsp
ValValVal
ProProPro
ValValGlu
TyrTyrTyr
ThrThr
Asp
LysLysLys
AspAspAsp
LysLysLys
LeuLeuLeu
ProProGlu
AspAspGlu
ProProPro
ProProPro
LysLysLys
LeuLeuLeu
LeuLeuLeu
ValValAla
ValValLeu
GluGluGlu
TryTryTry
AspAspGly
ValValVal
LysLysLys
HisHisHis
CysCysLeu
GluGluGlu
ValValVal
ThrThrThr
Ala'ValAla ValAla Val
LeuLeuLeu
GlyGlyGly
ValValVal
ValValVal
AlaAlaAla
GlyGlyGly
GluGluGlu
GlyGlyHis
ThrThrThr
AspAspAsp
LeuLeuVal
AlaAlaSer
GlyGlyGly
ArgArgArg
MetMetMet
AlaAlaSer
PhePhePhe
ProProPro
AlaAlaAla
TyrTyrTyr
GluGluGlu
PhePhePhe
GlyGlyGly
PhePhePhe
AlaAlaAla
GluGluGlu
HisHis
Arg
GluGluGlu
AlaAlaAla
PhePhePhe
AspAspAsp
SerSerGly
ThrThrAla
AspAspAsp
HisHisHis
LysLysLys
LeuLeuLeu
GluGluAsp
ProProPro
AspAspGlu
LeuLeuLeu
PhePhePhe
PhePhePhe
ValValVal
GlyGlyGly
ArgArgArg
SerSerSer
PhePhePhe
LysLysLys
ValValVal
GlyGlyGly
LeuLeuVal
Ser'SerSer
GluGluGlu
ArgLeu
Arg
LeuLeuLeu
GlyGlyGly
LysLysLys
ValValVal
AlaAlaAla
FIGURE 2
Human: Val His Leu Thr Pro Glu Glu Lys, Ser Ala Val Thr Ala Leu TryGorilla: Val His Leu Thr Pro Glu Glu Lys Ser Ala Val Thr ' Ala Leu TryHorse: Val Glu Leu Ser Gly Glu Glu Lys Ala Ala Val Leu Ala Leu Try
Human: Gly Val Ala Asp Ala Leu Ala His Lys Tyr HisGorilla: Gly Val Ala Asp Ala Leu Ala His' Lys Tyr His
Horse: Gly Val Ala Asp Ala Leu Ala His Lys Tyr His
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Name Period Date
Check your answers. Each column should total 146.
Analysis1. Where is hemoglobin normally found?
2. Circle those words which correctly apply to or describe hemoglobin:
protein composed of amino acids chemical molecule composed of DNA carbohydrate
3. How many different kinds of amino acids are present in these three animals' hemoglobin?
4. (a) Which amino acid is most common in all three animals?
(b) Which amino acid is next most common in all three animals?
(c) Which amino acid is the least common in all three animals?
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TABLE2. NUMBER Of EACH AMINO ACID
AMINO ACID ABBREVIATION HUMAN GORIlLLA HORSE
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
Name Period Date
5. Use your data from Table 1 to answer these questions. (use very similar, somewhat similar, not similar)
(a) How similar are the amino acid sequences of human and gorilla hemoglobin?
(b) How similar are human and horse hemoglobin?
(c) How similar are gorilla and horse hemoglobin?
6. Of the different types of amino acids found in hemoglobin, how many are present in the same exact number
(a) in humans and gorillas?
(b) in humans and horses?
(c) in gorillas and horses?
7. Onthe basisof youranswerto question6, (useverysimilar,somewhatsimilar,notsimilar)
(a) how similar is the chemical makeup of human and gorilla hemoglobin?
(b) how similar are human and horse hemoglobin?
(c) how similar are gorilla and horse hemoglobin?
8. Which two animals seem to have more similar hemoglobin?
9. The sequence of amino acids corresponds to the sequence of base molecules in DNA. Are the base sequences of DNA mostsimilar in human and gorilla, gorilla and horse, or human and horse?
10. In numbers, explain how the base sequences (genes) for hemoglobin formation on human chromosomes differ from thosein gorillas. (How many bases are different?)
11. What genetic mechanism may have been responsible for this base sequence change?
12. Give reasons for supporting or rejecting the following statement.
Upon examination, segments of human and gorilla DNA responsible for inheritance of hemoglobin should appear almost
chemically alike.
13. Give reasons for supporting or rejecting the following statement.
Evolutionary relationships are stronger between living organisms which have close biochemical (protein) similarities than
between living organisms which do not have close biochemical similarities.
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