Codon Decoder Stations Activity
STATION 1
DNA vs. RNA Showdown
Molecular Genetics • Structure & Differences
Rotation Time 4–5 Minutes
Key Biology Facts: Study Before Answering
DNA The Blueprint
- • Strands: 2 Strands (Double Helix ladder)
- • Sugar: Deoxyribose
- • Nitrogen Bases: A, T (Thymine), C, G
- • Home Base: Stays locked inside the NUCLEUS
RNA (mRNA) The Messenger
- • Strands: 1 Strand (Single ribbon)
- • Sugar: Ribose
- • Nitrogen Bases: A, U (Uracil), C, G
- • Job Location: Travels to the RIBOSOME
Big Difference Alert: RNA has NO Thymine (T). Whenever RNA pairs, it uses Uracil (U) instead!
In Your Science Journal: Record Station 1
Answer in full thoughts or complete sentences
Task 1 How many strands does DNA have? How many strands does RNA have?
Write: "DNA has ___ strands, while RNA has ___ strand."
Task 2 Which nitrogen base is found ONLY in RNA (never in DNA)?
Write: "The special base found only in RNA is _______ (Letter: ___)."
Task 3 Cell locations: Where does DNA stay, and where does mRNA travel to make proteins?
Write: "DNA stays in the __________, but mRNA travels out to the __________."
Task 4 (Quick Check) A student wrote an RNA code as A - T - G. What mistake did they make?
Codon Stations Activity • 9th Grade Biology When timer sounds ➔ Rotate to Station 2
STATION 2
Transcribe the Message
Molecular Genetics • DNA to mRNA Base Pairing
Rotation Time 4–5 Minutes
The Golden Base-Pairing Rules (Transcription)
DNA Base A pairs with U Uracil
DNA Base T pairs with A Adenine
DNA Base C pairs with G Guanine
DNA Base G pairs with C Cytosine
Worked Example Model:
DNA Template T - A - C
➔
mRNA Codon A - U - G
In Your Science Journal: Record Station 2
Transcribe DNA triplets into mRNA codons
Task 1 Fill in the blanks in your journal for the pairing rules:
• DNA A pairs with mRNA ____
• DNA T pairs with mRNA ____
• DNA C pairs with mRNA ____
• DNA G pairs with mRNA ____
Task 2 Transcribe these 4 DNA triplets into mRNA codons:
A. DNA: G - G - C ➔ mRNA: ___ - ___ - ___
B. DNA: C - A - T ➔ mRNA: ___ - ___ - ___
C. DNA: A - A - T ➔ mRNA: ___ - ___ - ___
D. DNA: C - G - A ➔ mRNA: ___ - ___ - ___
Task 3 Spot the Trap: If DNA has the letter A, why can you NEVER write T on the mRNA strand?
Codon Stations Activity • 9th Grade Biology When timer sounds ➔ Rotate to Station 3
STATION 3
The Square Codon Table
Translating mRNA to Amino Acids • Grid Navigation
Rotation Time 4–5 Minutes
STEP 1: LEFT SIDE Find 1st letter ➔ Locks your ROW
STEP 2: TOP SIDE Find 2nd letter ➔ Locks your COLUMN
STEP 3: RIGHT SIDE Find 3rd letter ➔ Finds AMINO ACID
| 1st BASE (LEFT) |
2nd BASE (TOP COLUMN) |
3rd BASE (RIGHT) |
|
U |
C |
| --- |
--- |
--- |
| U |
|
|
| UUU: Phe |
|
|
UUC: Phe
UUA: Leu
UUG: Leu
|
UCU: Ser
UCC: Ser
UCA: Ser
UCG: Ser
|
UAU: Tyr
UAC: Tyr
UAA: STOP
UAG: STOP
|
UGU: Cys
UGC: Cys
UGA: STOP
UGG: Trp
| U
C
A
G |
| C |
CUU: Leu
CUC: Leu
CUA: Leu
CUG: Leu
|
CCU: Pro
CCC: Pro
CCA: Pro
CCG: Pro
|
CAU: His
CAC: His
CAA: Gln
CAG: Gln
|
CGU: Arg
CGC: Arg
CGA: Arg
CGG: Arg
| U
C
A
G |
| A |
AUU: Ile
AUC: Ile
AUA: Ile
AUG: Met (START)
|
ACU: Thr
ACC: Thr
ACA: Thr
ACG: Thr
|
AAU: Asn
AAC: Asn
AAA: Lys
AAG: Lys
|
AGU: Ser
AGC: Ser
AGA: Arg
AGG: Arg
| U
C
A
G |
| G |
GUU: Val
GUC: Val
GUA: Val
GUG: Val
|
GCU: Ala
GCC: Ala
GCA: Ala
GCG: Ala
|
GAU: Asp
GAC: Asp
GAA: Glu
GAG: Glu
|
GGU: Gly
GGC: Gly
GGA: Gly
GGG: Gly
| U
C
A
G |
In Your Science Journal: Record Station 3
Decode using the square table above
1. Codon: U - U - C
Row: U | Col: U | 3rd: C ➔ Amino Acid: _______
2. Codon: G - C - A
Row: G | Col: C | 3rd: A ➔ Amino Acid: _______
3. Codon: C - A - G
Row: C | Col: A | 3rd: G ➔ Amino Acid: _______
4. Codon: A - U - G
Universal START Codon ➔ Amino Acid: _______
Codon Stations Activity • 9th Grade Biology When timer sounds ➔ Rotate to Station 4
STATION 4
The Circular Codon Wheel
Inside-to-Outside Translation • Radial Navigation
Rotation Time 4–5 Minutes
1
Center Hub (5'): 1st Base (U, C, A, or G)
➔
2
Middle Ring: 2nd Base
➔
3
Outer Ring: 3rd Base ➔ Read Amino Acid on Rim!
5' U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G U C A G Leucine (Leu) Proline (Pro) His Gln Arginine (Arg) Ile Met* Threonine (Thr) Asn Lys Ser Arg Valine (Val) Alanine (Ala) Asp Glu Glycine (Gly) Phe Leu Serine (Ser) Tyr STOP Cys STOP Trp
Top-Left Hub: U Phe, Leu, Ser, Tyr, Cys, Trp, STOP
Top-Right Hub: C Leu, Pro, His, Gln, Arg
Bottom-Right Hub: A Ile, AUG (Met/START), Thr, Asn, Lys
Bottom-Left Hub: G Val, Ala, Asp, Glu, Gly
In Your Science Journal: Record Station 4
Trace from center hub ➔ outward to outer rim
1. Codon: A - C - U
Center: A ➔ Middle: C ➔ Outer: U ➔ Amino Acid: _______
2. Codon: G - G - G
Center: G ➔ Middle: G ➔ Outer: G ➔ Amino Acid: _______
3. Codon: U - A - U
Center: U ➔ Middle: A ➔ Outer: U ➔ Amino Acid: _______
4. Direction Rule Question:
Do you read the codon wheel Inside ➔ Out OR Outside ➔ In?
Codon Stations Activity • 9th Grade Biology When timer sounds ➔ Rotate to Station 5
STATION 5
The Full Protein Pipeline
DNA ➔ mRNA ➔ Amino Acid (Central Dogma Mission)
Rotation Time 4–5 Minutes
The Cell's Protein Assembly Line
1. DNA Template T - A - C Inside Nucleus
Transcribe
2. mRNA Codon A - U - G Travels to Ribosome
Translate
3. Amino Acid Methionine Building Block
Codon Reference:
AUG = Methionine
GGU = Glycine
CUA = Leucine
UGA = STOP
In Your Science Journal: Record Station 5
Solve the Secret Peptide Code!
Target DNA Gene Sequence to Crack:
T A C | C C A | G A T
Step 1: Transcribe Write the matching mRNA codon for each DNA triplet in your journal:
Codon 1: TAC ➔ ___ ___ ___
Codon 2: CCA ➔ ___ ___ ___
Codon 3: GAT ➔ ___ ___ ___
Step 2: Translate Use the chart (or reference key above) to find the 3 Amino Acids:
Write in your journal: Amino Acid 1: _______ ➔ Amino Acid 2: _______ ➔ Amino Acid 3: _______
Step 3: Synthesis What biological molecule did your ribosome just build by linking amino acids together?
Codon Stations Activity • 9th Grade Biology When timer sounds ➔ Rotate to Station 6
STATION 6
Start & Stop Signals
Traffic Lights of the Ribosome • Mutation Spotter
Rotation Time 4–5 Minutes
The Ribosome's Traffic Signals
GREEN LIGHT: START 1 Codon
A - U - G Codes for Methionine (Met)
Tells the ribosome: "Attach here and begin assembling the protein chain!"
RED LIGHT: STOP 3 Codons
UAA | UAG | UGA
NO Amino Acid! Tells ribosome: "Protein finished! Release chain now!"
Fun Memory Trick for the 3 Stop Codons: UAA = U Are Away | UAG = U Are Gone | UGA = U Go Away!
In Your Science Journal: Record Station 6
Answer all 3 challenges
Task 1 What is the universal START codon? What amino acid does it add to the chain?
Write: "The start codon is _______ and it codes for ____________."
Task 2 Name all THREE stop codons. Do stop codons add an amino acid?
Write: "The three stop codons are ___, ___, and ___. They (do / do NOT) add an amino acid."
Task 3 (Traffic Cop Challenge) Look at this mRNA strand traveling through a ribosome:
5' ➔ AUG (Met) ➔ GAU (Asp) ➔ UUU (Phe) ➔ UAG ➔ CCU (Pro)
Question: Which codon signals the ribosome to STOP? Will the cell ever add Proline (CCU) to this protein? Why or why not?
Codon Stations Activity • 9th Grade Biology Station 6 Complete! Return to your seat for debrief.
Optional Student Handout / Journal Layout Guide
Codon Station Activity Journal Sheet
Name:
Period: Date:
STATION 1: DNA vs. RNA
1. DNA has ____ strands. RNA has ____ strand.
2. Base ONLY in RNA:
3. DNA stays in: | RNA goes to:
4. Student mistake:
STATION 2: Transcribe (DNA ➔ mRNA)
1. A➔__ | T➔__ | C➔__ | G➔__
A. GGC ➔ ______
B. CAT ➔ ______
C. AAT ➔ ______
D. CGA ➔ ______
3. Why no T on RNA?
STATION 3: Square Codon Table
1. UUC ➔ Amino Acid:
2. GCA ➔ Amino Acid:
3. CAG ➔ Amino Acid:
4. AUG ➔ Amino Acid: (START)
STATION 4: Circular Codon Wheel
1. ACU ➔ Amino Acid:
2. GGG ➔ Amino Acid:
3. UAU ➔ Amino Acid:
4. Read wheel: Circle: [ Inside ➔ Out ] or [ Out ➔ Inside ]
STATION 5: Secret Protein Mission
DNA: TAC | CCA | GAT
mRNA: ___ | ___ | ___
Protein Chain:
What did we build? A chain.
STATION 6: Start & Stop Signals
1. START Codon: _______ (Acid: )
2. THREE Stop Codons: ____, ____, ____
3. In the challenge, codon ______ stopped it.
4. Did cell make Proline? (Yes / No) Why:
Biology Station Activity • Journal Recording Page Turn into teacher or tape directly into interactive science notebook
Teacher Resource
Answer Key & Facilitation Guide
Activity Duration: 30 Minutes 6 Stations × 4–5 Mins + Debrief
Station 1: DNA vs. RNA
- Task 1: DNA has 2 strands; RNA has 1 strand.
- Task 2: Uracil (U) is only in RNA (replaces Thymine).
- Task 3: DNA stays in the Nucleus; mRNA travels to the Ribosome.
- Task 4: RNA never has Thymine (T); it should have been
A - U - G.
Station 2: Transcription
- Task 1: A➔U | T➔A | C➔G | G➔C
- Task 2A: DNA
GGC ➔ mRNA CCG
- Task 2B: DNA
CAT ➔ mRNA GUA
- Task 2C: DNA
AAT ➔ mRNA UUA
- Task 2D: DNA
CGA ➔ mRNA GCU
- Task 3: RNA uses Uracil (U) instead of Thymine (T).
Station 3: Square Codon Table
- Task 1:
UUC ➔ Phenylalanine (Phe)
- Task 2:
GCA ➔ Alanine (Ala)
- Task 3:
CAG ➔ Glutamine (Gln)
- Task 4:
AUG ➔ Methionine (Met) (Universal Start)
Station 4: Circular Codon Wheel
- Task 1:
ACU ➔ Threonine (Thr)
- Task 2:
GGG ➔ Glycine (Gly)
- Task 3:
UAU ➔ Tyrosine (Tyr)
- Task 4: Always read Inside to Outside (Center hub ➔ Middle ring ➔ Outer ring).
Station 5: Secret Protein Mission
- Step 1 (mRNA):
AUG | GGU | CUA
- Step 2 (Amino Acids): Methionine (Met) ➔ Glycine (Gly) ➔ Leucine (Leu)
- Step 3 (Synthesis): Built a Protein (or polypeptide / peptide chain).
Station 6: Start & Stop Signals
- Task 1: START codon is
AUG (Codes for Methionine).
- Task 2:
UAA, UAG, UGA (They do NOT add an amino acid).
- Task 3: Codon
UAG signals stop. No, the ribosome detaches when it hits STOP, so Proline is never added!
Common Student Misconceptions to Watch For:
• Writing 'T' in mRNA: Remind students of the "Rule of U": if they write 'T' on mRNA, it is always wrong!
• Reading the wheel backwards: Watch Station 4 to ensure students start at the small center circle, not the outer ring.
• Transcribing vs Translating: Students often try to look up DNA directly on the codon chart. Remind them: Codon charts only speak mRNA!
• Stop codon meaning: Students may think STOP codons code for an amino acid named "Stop". Clarify that it is a punctuation mark (period).
Teacher Answer Key • Codon Decoder Stations Activity Genetics Unit • Molecular Biology