BIOLOGY: BREAKING THE CODE
Name_____________________
Date________________Per.___
I. REPLICATION
For each of the three DNA sequences below, write the sequence of the complementary strand of
DNA that results after replication.
DNA molecule #1: T A C C G G A T G C C A G A T C A A A T C
Complementary DNA #1_________________________________________________________
DNA molecule #2: T A C G G G G G C G T A A C C CA A C T
Complementary DNA #2_________________________________________________________
DNA molecule #3: T A C C T G T T A G C T A C A A A A T T
Complementary DNA #3_________________________________________________________
II. TRANSCRIPTION
For each of the same DNA sequences below, write the sequence of messenger RNA (mRNA)
codons that is synthesized during transcription. Be sure to separate the codons into triplets.
DNA molecule #1: T A C C G G A T G C C A G A T C A A A T C
mRNA #1 _____________________________________________________________
DNA molecule #2: T A C G G G G G C G T A A C C A C A A C T
mRNA #2______________________________________________________________
DNA molecule #3: T A C C T G T T A A G C T A C A A A A T T
mRNA #3______________________________________________________________
III.TRANSLATION
For each of the mRNA codon sequences you have written from II., determine the sequence of
transfer RNA (tRNA) anticodons that match it.
mRNA #1 __________________________________________________________
Anticodons for mRNA #1: _________________________________________________________
mRNA #2__________________________________________________________________
Anticodons for mRNA #2: _________________________________________________________
mRNA #3__________________________________________________________
Using the chart or circle, write the amino acid sequence coded for by each mRNA.
(Note: The code is based on mRNA codons, not tRNA anticodons.)
Polypeptide #1: _________________________________________________________________
Polypeptide #2: _________________________________________________________________
Polypeptide #3: _________________________________________________________________
Vocabulary:
Replication - Synthesis of an identical copy of a DNA strand.
Transcription - Synthesis of mRNA molecule. (codon)
Translation - Synthesis of polypeptides (amino acids/peptide bonds) from tRNA/ amino acids/ (anticodons)
Codon - Base triplet on mRNA.
Anticodon - Complementary triplet on tRNA.
Polypeptide - Protein molecule
Procedure: Protein synthesis = a "fairy tale."
Fairy Tale: Title=__________________________________________________________
"Once upon a time there were two fraternal twin brothers: Donald N. Armstrong and Ronald N. Armstrong.
Donald was the larger of the two, and he was a successful inventor with many patents. Although Ronald was
not as big as his brother, he was extremely loyal. One day Donald came up with an idea for a solar powered
car. Given the ever-present possibility of energy shortage, an efficient solar powered car would be in great
demand. However, Donald really didn't want to leave his comfortable estate. He certainly couldn't take a
chance by using e-mail or a fax to send his plans to the factory. They might be stolen by industrial spies! Or
messed up in some way…. Donald knows his loyal brother would do anything for him, so he asks him to be a
messenger and carry the plans to the factory. At the factory, the assembly line is set up and factory workers
bring the parts to assemble the prototype. The car proves to be enormously successful. The Armstrong
brothers buy an even bigger estate and live happily ever after!"
Relate each part of the story to the corresponding component of the process of protein synthesis:
Donald: DNA____________________
Ronald: _______________________
estate: ________________________
plans: _________________________
factory:__________________________
factory workers: ___________________
car:______________________________
1. What are the 3 differences between DNA and RNA?
2. Explain the process of DNA replication.
3.Explain the process of transcription and mRNA codons.
4. Explain the process of translation and tRNA anticodons.
5. Explain how to use the chart and/or circle to determine polypeptide sequence from RNA codons.
PROTEIN SYNTHESIS
Name___________________
Date________________Per._____
Protein synthesis is a complex process. You will trace the steps that are involved in the protein synthesis of a
part of a molecule of oxytocin. Oxytocin is the pituitary hormone that helps regulate blood pressure, stimulates
the uterus to contract during childbirth, and stimulates the production of milk after childbirth.
A. Protein synthesis begins with DNA in the nucleus. Below is a DNA sequence that could code for part of a
molecule of oxytocin.
 Write the sequence of messenger RNA (mRNA) codons that would result from the transcription of
this portion of DNA . The arrow marks the starting point
(Nucleus) DNA
ACA - ATA - TAG - CTT - TTG - ACG - GGG - AAC - CCC - ATT
1
2
3
4
5
6
7
8
9
10
TRANSCRIPTION:
1
2
3
4
5
6
7
8
9
10
mRNA: (Codon)
UGU – UAU_______________________________________________________
B. After transcription (in nucleus), mRNA attaches to a
START: Intiator Codon (AUG)
ribosome where translation (in cytoplasm )
takes place. Each codon of mRNA bonds with an anticodon of a transfer RNA (tRNA) and each tRNA molecule
bonds with a specific amino acid. The table below shows the mRNA codons and the amino acids for which they
code. For example, if you were given the codon AGA, you can see from the table
that these bases code for the amino acid arginine.
STOP: terminator Codon (UAA,UAG,UGA)
1. UGU
2. UAU
AUG:
Methionine
(start)
3.
4.
5.
6.
7.
8
9.
10.

Use the mRNA sequence from A to write the sequence (1 –10) of amino acids in this
part of the oxytocin molecule.
TRANSLATION (Cytoplasm) on Ribosomes
1
2
- 3
Cysteine - Tyrosine _______________________________________________________________________________________
_______________________________________________________________________________________
1. How many amino acids make up this portion of the oxytocin molecule? ___________________________
2. What is the purpose of the UAA codon? ____________________________________________________
C. In order to get another view of the entire process of protein synthesis, label the structures on the
diagram below. (ribosome (rRNA), mRNA [codon=3 bases], tRNA [anticodon=3 bases], protein, DNA
To complete the chart below, give the name and a brief description of each step in protein synthesis that
occurs in the part of the cell shown in the diagram above.
PART OF CELL Name of Protein Synthesis Process
Description
Nucleus
ribosome
cytoplasm
NOW PUT IT ALL TOGETHER: RNA MAUFACTURE AND USE IN THE CELL: Color Code and label
1. In the following diagram: LABEL: messenger RNA (mRNA), transfer RNA (tRNA),
ribosomal RNA (rRNA), amino acid, Codon, anti-codon and fill in the correct BASES: (A,G, C, U)
R I
B
O S
O M
E
2. Where would the PEPTIDE BONDS be located? (Color code GREEN)
3. Four different kinds of amino acids are represented in the diagram by different shaped labeled a, b, c and d.
Study the diagram and decide whether the next two places along the chain will be filled by any of these
amino acids or by still other kinds. DRAW AND LABEL THE NEXT two amino acids, using new shapes
and letters if necessary.