Name:
Date:
Period:
Protein Synthesis
13.3A
Use the chart of the genetic code given at the right and the notes given to you below to answer
the questions that follow. You may also have to refer to your textbook or notes for help.
Reading the Chart:
•The first base in a codon is the
largest most center letter in the
chart.
•The second base in a codon is the
medium size letter just outside
the first bases.
•The third base in a codon is the
smallest size letter next to the
words of the amino acids.
***Translation begins at the first
“start” codon (AUG or Met) and
ends when a “stop” codon is
reached.
Ex: Methionine (located towards
the bottom of the wheel) is AUG.
1. Transcribe the entire section of DNA below into mRNA. Use the top strand for
transcription.
DNA
mRNA
T A C-A T A-C C A-T T A-G C T-T G C-C A T-A C T-A A
A T G-T A T-G G T-A A T-C G A-A C G-G TA-T G A-T T
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2. Translate the mRNA sequence above into the appropriate amino acid sequence
(protein/polypeptide). Remember to start on Met and stop on the right codon.
Amino Acid
Sequence
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3. Go through transcription and translation to give the appropriate amino acid sequence for
the DNA molecules below. Like before, use the top strand for translation. Transcribe the
entire sequence but only translate the sequence after the “start” codon.
DNA
A C C-T A C-A T G-A C A-T T G-A A A-A T T-T C
T G G-A T G-T A C-T G T-A A C-T T T- T A A-A G
mRNA
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Amino Acid
Sequence
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4. Now work backwards from the amino acid sequence below to generate the appropriate
mRNA molecule. There will be several different possible answers because more than one
codon can stand for a single amino acid.
Amino Acid
Sequence
mRNA
Met - Pro - Lys - Thr - stop
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5. Use the mRNA sequence you generated above to determine the corresponding DNA
molecule. Hint: Generate the corresponding single strand first from mRNA and then fill in
the complimentary strand to make the DNA double helix. Remember, DNA has thymine
and RNA has uracil.
DNA First
Strand
DNA Complimentary Strand
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Protein Synthesis – More Transcription and Translation
Transcription (DNA → mRNA)
Use the summary of transcription below as well as information
gathered in your notes to answer the questions that follow.
Transcription:
DNA double helix unwinds.
RNA copy made from DNA template.
RNA is edited before exiting the nucleus.
Questions:
6. Summarize in your own words transcription. ______________________________________
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7. Where does transcription occur? Why must it occur in this location? ___________________
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8. Fill in the correct base for the complimentary RNA strand.
DNA strand
RNA strand
Guanine (G)
______________
Adenine (A)
______________
Thymine (T)
______________
Cytosine (C)
______________
9. Give the appropriate mRNA strand that would be transcribed from the DNA strand below.
DNA strand:
T
A
T
A
A
T
A
C
T
C
G
A
C
A
A
T
T
mRNA strand: _______________________________________________________________
Translation (mRNA  AA chain/Polypeptide chain/Protein)
Use the summary of translation below as well as information gathered in your notes to answer the
questions that follow.
Translation:
mRNA start codon binds to ribosome.
tRNA picks up AA in cytoplasm and carries it to ribosome.
tRNA anticodon binds to complimentary mRNA codon.
AA attaches to end of growing polypeptide chain.
tRNA leaves to find another AA.
Translation ends when stop codon is reached.
Polypeptide released for folding.
Questions:
10. Describe, in your own words, translation: _________________________________________
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11. Where does translation occur? Why must it occur in this location? ____________________
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12. Describe, in your own words, genetic code: _______________________________________
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13. What is a codon? What is an anticodon? _________________________________________
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14. Use the AA chart from page 1 (front page) to answer this question.
A. Match the following codons with the AA they code. The first one is done for you.
GCU
Alanine_____
AAG
___________
CAA
___________
UUU
___________
UGG
___________
AUG
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15. What codon(s) code for the Amino Acid lysine (Lys)? For valine (Val)?
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16. What are the 3 stop codons? What do stop codons do? What is the start codon?
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Below are two partial sequences of DNA bases (shown for only one strand of DNA) Sequence 1 is
from a human and sequence 2 is from a cow. In both humans and cows, this sequence is part of a
set of instructions for controlling a bodily function. In this case, the sequence contains the gene to
make the protein insulin. Insulin is necessary for the uptake of sugar from blood. Without insulin, a
person cannot digest sugars the same way others can, and they have a disease called diabetes.
Instructions: For both the human and the cow sequences, make complimentary RNA strands for the
DNA shown. Remember to substitute U’s for T’s when transcribing RNA. Use the codon table on
the front page to translate the amino acid sequences to make the insulin proteins.
17. Sequence 1 – Human
DNA : T A C C C A T A G C A C G T T A C A A C G T G A A G G A T T
mRNA : _______________________________________________________________________
Amino Acids: __________________________________________________________________
18. Sequence 2 – Cow
DNA : T A C C C G T A G C A T G T T A C A A C G C G A A G G A T T
mRNA: _______________________________________________________________________
Amino Acids: __________________________________________________________________
19. The DNA sequence is different for the cow and the human, but the amino acid chain
produced by the sequence is almost the same. How can humans and cows have amino acid
chains that are similar?
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20. Could two humans (or two cows) have some differences in the DNA sequence for insulin, yet
still make exactly the same insulin proteins? Explain.
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