Codon Decoder Worksheet
Biology • Molecular Genetics Front Side: Guided Practice
Protein Codebreaker Worksheet
Mastering the Square mRNA Codon Table for Translation
Name:
Date: Period:
The Central Dogma Flow:
DNA (Replication) ➔ mRNA (Transcription) ➔ Protein (Translation)
Standard Square mRNA Codon Table
*Codons are read 5' to 3' on mRNA
| 1st Base
(Left) | 2nd Base (Top of Table) | 3rd Base
(Right) |
| --- | --- | --- |
| U |
C |
A |
G |
| U |
|
|
|
| UUU: Phenylalanine (Phe) |
|
|
|
UUC: Phenylalanine (Phe)
UUA: Leucine (Leu)
UUG: Leucine (Leu)
|
UCU: Serine (Ser)
UCC: Serine (Ser)
UCA: Serine (Ser)
UCG: Serine (Ser)
|
UAU: Tyrosine (Tyr)
UAC: Tyrosine (Tyr)
UAA: STOP
UAG: STOP
|
UGU: Cysteine (Cys)
UGC: Cysteine (Cys)
UGA: STOP
UGG: Tryptophan (Trp)
|
U
C
A
G
|
| C |
CUU: Leucine (Leu)
CUC: Leucine (Leu)
CUA: Leucine (Leu)
CUG: Leucine (Leu)
|
CCU: Proline (Pro)
CCC: Proline (Pro)
CCA: Proline (Pro)
CCG: Proline (Pro)
|
CAU: Histidine (His)
CAC: Histidine (His)
CAA: Glutamine (Gln)
CAG: Glutamine (Gln)
|
CGU: Arginine (Arg)
CGC: Arginine (Arg)
CGA: Arginine (Arg)
CGG: Arginine (Arg)
|
U
C
A
G
|
| A |
AUU: Isoleucine (Ile)
AUC: Isoleucine (Ile)
AUA: Isoleucine (Ile)
AUG: Methionine (START)
|
ACU: Threonine (Thr)
ACC: Threonine (Thr)
ACA: Threonine (Thr)
ACG: Threonine (Thr)
|
AAU: Asparagine (Asn)
AAC: Asparagine (Asn)
AAA: Lysine (Lys)
AAG: Lysine (Lys)
|
AGU: Serine (Ser)
AGC: Serine (Ser)
AGA: Arginine (Arg)
AGG: Arginine (Arg)
|
U
C
A
G
|
| G |
GUU: Valine (Val)
GUC: Valine (Val)
GUA: Valine (Val)
GUG: Valine (Val)
|
GCU: Alanine (Ala)
GCC: Alanine (Ala)
GCA: Alanine (Ala)
GCG: Alanine (Ala)
|
GAU: Aspartic acid (Asp)
GAC: Aspartic acid (Asp)
GAA: Glutamic acid (Glu)
GAG: Glutamic acid (Glu)
|
GGU: Glycine (Gly)
GGC: Glycine (Gly)
GGA: Glycine (Gly)
GGG: Glycine (Gly)
|
U
C
A
G
|
Overhead Guide: 3 Steps to Read Any Codon (Example: C-A-G)
Step 1: First Base (Left)
Find the 1st letter on the LEFT column. This locks you into one of the 4 big rows.
Ex: 'C' ➔ Row 2
Step 2: Second Base (Top)
Find the 2nd letter on the TOP. Move across to where that column intersects your row.
Ex: 'A' ➔ Box (Row C, Col A)
Step 3: Third Base (Right)
Find the 3rd letter on the RIGHT to pinpoint the exact amino acid inside that box.
Ex: 'G' ➔ Glutamine (Gln)
Guided Practice
Follow-Along with Teacher on Projector
Fill in each step as we trace the chart together
1. Codon: AUG Universal START
1st Base (Row):
2nd Base (Column):
3rd Base (Row item):
Amino Acid:
2. Codon: G-C-U Standard
1st Base (Row):
2nd Base (Column):
3rd Base (Row item):
Amino Acid:
3. Codon: U-A-A Signal
1st Base (Row):
2nd Base (Column):
3rd Base (Row item):
Amino Acid / Signal:
Turn over for Part 2: Independent Decoding & Translation Mission PAGE 1 (FRONT)
Independent & Partner Practice
Translation Lab: Cracking the Genetic Code
Use Codon Table on Front Side
PAGE 2 (BACK)
1
Rapid Codon Warm-Up
(Flip to the front table to find the amino acid or signal)
| mRNA Codon |
Amino Acid Name (Full or 3-Letter) |
mRNA Codon |
Amino Acid Name (Full or 3-Letter) |
| A. U-U-C |
|
|
|
| D. C-A-A |
|
|
|
|
| B. G-G-A |
| E. U-G-A |
|
| C. A-C-G |
| F. A-U-G |
|
2
The Full Molecular Pipeline: DNA ➔ mRNA ➔ Protein
Remember RNA rules: A pairs with U!
Gene Sequence Alpha (Cellular Hormone Peptide) Transcribe then translate (5 codons)
DNA Template:
TAC | CGA | TGT | CTA | ACT
mRNA Codons:
|
|
|
|
Amino Acids:
➔
➔
➔
➔
Gene Sequence Beta (Case Study: Premature Stop Mutation) Watch for what happens at Codon 4!
DNA Template:
TAC | AAG | GGT | ATC | CGT
mRNA Codons:
|
|
|
|
Amino Acids:
➔
➔
➔
➔
3
Targeted Translation Practice Drills
(Use the front table for forward and reverse lookups)
A. Reverse Decoding: Write ONE valid mRNA codon for each amino acid: (Some have multiple right answers!)
1. Tryptophan (Trp):
2. Histidine (His):
3. Proline (Pro):
4. Lysine (Lys):
B. Translate this 5-codon mRNA strand directly into its amino acid sequence: 5' - AUG - GAU - UUU - CCU - UAG - 3'
Codon 1: AUG
Codon 2: GAU
Codon 3: UUU
Codon 4: CCU
Codon 5: UAG
C. Stop Signal Spotter: Write down the three mRNA codons that signal STOP (termination):
1:
2:
3:
Teacher Exit Stamp / Score: ____________ / 25 pts
Genetics Unit • Translation & Codon Decoding