Download Decoding the message_2 - Molecular-Biology-Resource

SAY IT WITH DNA: PROTEIN SYNTHESIS WORKSHEET
Category
Resource type
Basic Concepts of Science
Dry lab
Scientific Investigation Skills and
Career Exploration
A1.11 communicate ideas, plans,
procedures, results, and conclusions
orally, in writing, and/or in
electronic presentations, using
appropriate language and a variety
of formats
Prior Knowledge
Students have an understanding of:
 The Central Dogma
 Basepairing in DNA vs. RNA
 Splicing
 Redundancy in the genetic code
Overall Expectations
Specific Expectations
D2 Investigate, through
laboratory activities the
structures of cell components and
their roles in processes that occur
within the cell
D2.1 use appropriate terminology related
to molecular genetics
D2.2 analyse a simulated strand of DNA to
determine the genetic code and base
pairing of DNA
D3.3 explain the steps involved in the
process of protein synthesis and how
genetic expression is controlled in
prokaryotes and eukaryotes
Student Learning Goals
By the end of the activity students will be to:
 Identify the amino acid that is coded by a given DNA
sequence
 Identify the DNA sequence from a strand of amino
acids in a polypeptide
Teacher’s Notes
Directions
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Suggestions
Limitations
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Modifications
for special
need students
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Resource(s)
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This activity is to be completed after the students have learned about the central dogma,
which is a fundamental and basic concept in molecular genetics. It is intended to review
and solidify the concept that the genetic code provides the instructions for protein
synthesis.
This is an AfL activity to ensure that students understand the central dogma.
In the chart below is the “DNA to amino acid dictionary.” Teachers can use this to make
their own personalized messages for the students
Review base pairing in DNA (A with T and G with C) vs. RNA (A with U and G with C)
This activity can also be done backwards (from translation to transcription); students will
learn how to determine the DNA sequences for a polypeptide/protein
This activity drastically simplifies how protein synthesis occurs.
o it does not accurately represent how DNA transcription occurs in eukaryotes since
it leaves out mRNA processing (e.g. splicing out of introns);
o It does not include other cell components (e.g. RNA polymerase, ribosomes) that
are involved in DNA transcription and translation;
Students should notice that methionine is found in the middle of certain DNA sequences or
not at all in the questions. Students should be reminded that methionine signals for
ribosomal translation.
Make sure to go over the instructions as well as repeating the instructions several times
Allow more time for students to complete the activity. For example, if the teacher chooses
to ask the students to create their own messages, the message swop can be completed
next class. This also gives students more time to ask the teacher questions one-on-one if
need be.
This activity was adopted and modified from:
http://www.indiana.edu/~ensiweb/connections/genetics/dna.les.html
DNA to Amino Acid Dictionary
Letter
A
A
A
A
C
C
D
D
E
E
F
F
G
G
G
G
DNA
codon
CGA
CGC
CGG
CGT
ACA
ACG
CTA
CTG
CTC
CTT
AAA
AAG
CCA
CCC
CCG
CCT
AA
Letter
Ala
Ala
Ala
Ala
Cys
Cys
Asp
Asp
Glu
Glu
Phe
Phe
Gly
Gly
Gly
Gly
H
H
I
I
I
K
K
L
L
L
L
L
L
M
N
N
DNA
codon
GTA
GTG
TAA
TAG
TAT
TTC
TTT
AAC
AAT
GAA
GAC
GAG
GAT
TAC
TTA
TTG
AA
Letter
His
His
His
Iso
Iso
Lys
Lys
Leu
Leu
Leu
Leu
Leu
Leu
Met
Asn
Asn
O
P
P
P
P
Q
Q
R
R
R
R
R
R
S
S
S
DNA
codon
ACT
GGA
GGC
GGG
GGT
GTC
GTT
GCA
GCC
GCG
GCT
TCC
TCT
AGA
AGC
AGG
AA
Letter
Pro
Pro
Pro
Pro
Glu
Glu
Arg
Arg
Arg
Arg
Arg
Arg
Ser
Ser
Ser
S
S
S
T
T
T
T
V
V
V
V
W
Y
Y
Spc
Spc
DNA
codon
AGT
TCA
TCG
TGA
TGC
TGG
TGT
CAA
CAC
CAG
CAT
ACC
ATA
ATG
ATC
ATT
AA
Ser
Ser
Ser
Thr
Thr
Thr
Thr
Val
Val
Val
Val
Trp
Tyr
Tyr
-
SAY IT WITH DNA: PROTEIN SYNTHESIS WORKSHEET
DNA
RNA
transcription
Protein
translation
The Central Dogma states that DNA directs the synthesis of proteins by producing RNA via
transcription followed by ribosomal translation of RNA into polypeptides. In this activity, you will decode
sequences of DNA into "secret" messages.
PART A
Determine the “secret” message by transcribing and then translating the bases from the given strands of
DNA below (#1-3). Use the dictionary to determine the letter that corresponds to each tRNA codon. You
must record ALL your steps from transcription to translation, including the amino acids that correspond
to each tRNA codon.
For example:
Given DNA
CTT
mRNA
GAA
tRNA
CUU
Letter
E
Amino Acid
Glu
If you have done this correctly, the letters should spell out a message in English.
DICTIONARY
tRNA
AAA
AAC
AAG
AAU
ACA
ACC
ACG
ACU
AGA
AGC
AGG
AGU
AUA
AUC
AUG
AUU
AA Letter
Phe
F
Leu
L
Phe
F
Leu
L
Cys
C
Trp
W
Cys
C
Thr
O
Ser
S
Ser
S
Ser
S
Ser
S
Tyr
Y
spc
Tyr
Y
spc
-
Note:
AA = Amino Acid
Spc = “space”
tRNA
CAA
CAC
CAG
CAU
CCA
CCC
CCG
CCU
CGA
CGC
CGG
CGU
CUA
CUC
CUG
CUU
AA Letter
Val
V
Val
V
Val
V
Val
V
Gly
G
Gly
G
Gly
G
Gly
G
Ala
A
Ala
A
Ala
A
Ala
A
Asp
D
Glu
E
Asp
D
Glu
E
tRNA
GAA
GAC
GAG
GAU
GCA
GCC
GCG
GCU
GGA
GGC
GGG
GGU
GUA
GUC
GUG
GUU
AA
Leu
Leu
Leu
Leu
Arg
Arg
Arg
Arg
Pro
Pro
Pro
Pro
His
Glu
His
Glu
Letter
L
L
L
L
R
R
R
R
P
P
P
P
H
Q
H
Q
tRNA
UAA
UAC
UAG
UAU
UCA
UCC
UCG
UCU
UGA
UGC
UGG
UGU
UUA
UUC
UUG
UUU
AA Letter
Iso
I
Met
M
Iso
I
Iso
I
Ser
S
Arg
R
Ser
S
Arg
R
Thr
T
Thr
T
Thr
T
Thr
T
Asn
N
Lys
K
Asn
N
Lys
K
1) DNA: TGA GTG CTT ATT ACG CTC TTA TGC TCC CGC GAG ATC CTA ACT CCC TAC
mRNA:
tRNA :
AA:
letter:
DNA:CGT ATT TAA TCA ATC ACT TTG ATC TGG GTG CTC ATT TGC CTT AGGTGA
mRNA:
tRNA :
AA:
letter:
2) DNA : GGA GTG TAT GAA ATC CTA ACT ATT ACC CTC ATT GTA CGC CAG CTC
mRNA:
tRNA:
AA:
letter:
DNA : ATC TGT GTG CTT ATC TGC ACC CTT TTA TGT ATG ATT AAA TAT AAG
mRNA:
tRNA :
AA:
letter:
DNA : TGA GTG ATC ACTAAA AAA
mRNA:
tRNA :
AA:
letter:
PART B
Answer the questions below.
1) Several codons code for “spc”. Explain why this is an advantage or disadvantage for the organism.
2) Are the given strands of DNA from a eukaryotic or prokaryotic organism? Explain your answer.
3) Explain where translation would begin for:
a. DNA sequence #1 (same as above): TGA GTG CTT ATT ACG CTC TTA TGC TCC CGC
GAG ATC CTA ACT CCC TAC CGT ATT TAA TCA ATC ACT TTG ATC TGG GTG
CTC ATT TGC CTT AGGTGA
b. DNA sequence #2 (same as above): GGA GTG TAT GAA ATC CTA ACT ATT ACC CTC
ATT GTA CGC CAG CTC ATC TGT GTG CTT ATC TGC ACC CTT TTA TGT ATG ATT
AAA TAT AAG TGA GTG ATC ACTAAA AAA
4) Construct your own secret DNA message by working backwards in the space provided below (from
English  AA  tRNA  mRNA  DNA). This message will be handed in on a separate piece of paper
with ONLY the DNA sequence on it and then it will be randomly given out to one of your classmates to
decode. Keep in mind that the letters B, J, U, X, and Z cannot be used in your message. (CAUTION:
obscene or derogatory messages are not acceptable).
ANSWERS
1) DNA:TGA GTG CTT ATT ACG CTC TTA TGC TCC CGC GAG ATC CTA ACT CCC TAC
mRNA: ACUCAC GAA UAA UGC GAGAAU ACG AGG GCG CUC UAGGAU UGA GGG AUG
tRNA : UGA GUGCUU AUU ACG CUC UUAUGC UCC CGC GAG AUC CUA ACU CCC UAC
AA: Thr His Glu spc Cys Glu Asn Thr Arg Ala Leu spc Asp Thr Gly Met
letter: T H E
C
E
N T
R A
L
D
O G M
DNA:CGT ATT TAA TCA ATC ACT TTG ATC TGG GTG
mRNA: GCA UAAAUU AGU UAG UGA AACUAG ACC CAC
tRNA : CGU AUU UAA UCA AUC ACU UUGAUC UGG GUG
AA: Ala spc Iso Ser spc Thr Asn spc Thr His
letter: A
I
S
O
N
T
H
CTC ATT TGC CTT AGGTGA
GAGUAA ACG GAA UCC ACU
CUC AUUUGC CUU AGGUGA
Glu spc Thr Glu Ser Thr
E
T E
S T
2) DNA : GGA GTG TAT GAA ATC CTA ACT ATT ACC CTC ATT GTA CGC CAG CTC
mRNA: CCU CAC AUA CUU UAG GAU UGAUAA UGG GAG UAACAU GCG GUC GAG
tRNA: GGA GUGUAU GAA AUC CUA ACU AUU ACC CUC AUU GUA CGC CAG CUC
AA: Pro His Iso Leu spc Asp Thr spc Trp Glu spc His Ala Val Glu
letter: P H
I
L
D O
W E
H
A V
E
DNA :
mRNA:
tRNA :
AA:
letter:
ATC TGT GTG CTT ATC TGC ACC CTT TTA TGT ATG ATT AAA TAT AAG
UAGACA CAC GAA UAG ACG UGG GAA AAU ACA UAC UAA UUU AUA UUC
AUCUGU GUG CUU AUC UGC ACC CUU UUA UGU AUGAUU AAA UAU AAG
spc Thr His Glu spc Thr Trp Glu Asn Thr Tyr spc Phe Iso Phe
T
H E
T W E N
T
Y
F
I
F
DNA : TGA GTG ATC ACTAAA AAA
mRNA: ACU CAC UAG UGA UUUUUU
tRNA : UGA GUGAUC ACU AAA AAA
AA: Thr His spc Thr Phe Phe
letter: T
H
O
F
F
PART B
Answer the questions below.
1) Several codons code for “spc”. Explain why this is an advantage or disadvantage for the organism.
A change in a single base may not necessarily result in a change in amino acid. Therefore, it would be an
advantage for the organism to have multiple codons for “spc”. This is an example of redundancy.
2) Are the given strands of DNA from a eukaryotic or prokaryotic organism? Explain your answer.
The strands of DNA are from a prokaryotic organism because splicing was not required.
3) Explain where translation would begin for:
a. DNA sequence #1 (same as above): TGA GTG CTT ATT ACG CTC TTA TGC TCC CGC
GAG ATC CTA ACT CCC TAC CGT ATT TAA TCA ATC ACT TTG ATC TGG GTG
CTC ATT TGC CTT AGGTGA
Translation would begin at TAC, which is underlined above. Translation begins here because TAC
codes for methionine, which signals the initiation of translation for the ribosome.
b. DNA sequence #2 (same as above): GGA GTG TAT GAA ATC CTA ACT ATT ACC CTC
ATT GTA CGC CAG CTC ATC TGT GTG CTT ATC TGC ACC CTT TTA TGT ATG ATT
AAA TAT AAG TGA GTG ATC ACTAAA AAA
This sequence would not be translated since it lacks methionine (Met )to signal the initiation of
translation for the ribosome.
4) Construct your own secret DNA message by working backwards below (from English  AA  tRNA
 mRNA  DNA). This message will be handed in on a separate piece of paper with ONLY the DNA
sequence on it and then it will be randomly given out to one of your classmates to decode. Keep in
mind that the letters B, J, U, X, and Z cannot be used in your message. (CAUTION: obscene or
derogatory messages are not acceptable).
All students will have a different message.