Read A Codon Chart
Look up mRNA codons on a chart to name the amino acid, the start codon, and the stop codons.
- A codon is three bases: You must read the mRNA in groups of three to use the chart.
- Reading frame: Where you start reading sets the codons, so the frame must stay consistent.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
Practice plain lookups: read a codon, find its row on the chart, and write the amino acid: and recognize a stop codon when you hit one.
Using the codon chart, which amino acid does the mRNA codon UUU code for?
Approved| mRNA codon | Meaning |
|---|---|
| AUG | Methionine (Met) - START |
| UUU | Phenylalanine (Phe) |
| UGG | Tryptophan (Trp) |
| GCA | Alanine (Ala) |
| UAA | STOP |
| UAG | STOP |
| UGA | STOP |
- A.Phenylalanine (Phe)
- B.Stop signal, which adds no amino acid
- C.Tryptophan (Trp)
- D.Methionine (Met)
Show the worked solution ▾
Answer: A. Phenylalanine (Phe)
- Step 1: Find UUU: Locate UUU in the chart's codon column.
- Step 2: Read its amino acid: Across from UUU the chart lists Phenylalanine (Phe).
Why it's right: The chart shows UUU codes for Phenylalanine (Phe).
- B: The stop codons are UAA, UAG, and UGA, not UUU.
- C: Tryptophan is UGG, not UUU.
- D: Methionine is AUG, not UUU.
Aligned to Biotechnology Research and Experiments: codon lookup · reading level ~grade 9
An mRNA reads AUGGCAUGG. Split it into groups of three starting at the first base, then name what the SECOND group calls for.
Reviewed- A.Tryptophan (Trp), the last group of three bases
- B.Methionine (Met), the first group of three bases
- C.Phenylalanine (Phe), which does not appear in this strand
- D.Alanine (Ala), the middle group of three bases
Show the worked solution ▾
Answer: D. Alanine (Ala), the middle group of three bases
- Step 1: Split into threes: AUG, then GCA, then UGG.
- Step 2: Count to the second group: The second group of three is GCA.
- Step 3: Look it up: GCA calls for alanine.
Why it's right: Splitting AUGGCAUGG into threes gives AUG, GCA, UGG. The second group is GCA, which calls for alanine.
- A: Tryptophan comes from UGG, which is the third group here, not the second.
- B: Methionine comes from AUG, which is the first group here, not the second.
- C: Phenylalanine comes from UUU, and UUU never appears in this strand.
Aligned to Biotechnology Research and Experiments · reading level ~grade 9
- In Unit 2.2 Decoding a Diagnosis, this skill turns class evidence into a result another person can check.
Fill these in as you work through the lesson.
- Codon (three mRNA bases):
- Codon chart (the key from codon to amino acid):
- Start codon (AUG (Met)):
- Stop codon (UAA, UAG, or UGA):
- Reading frame (where you start grouping the bases):
Read the mRNA in groups of bases. The codon means start (Methionine). The codons UAA, UAG, and all mean stop.
- Which codon both starts a protein and codes for methionine?
- Name the three codons that mean stop.
- If you start reading at a different base, why do you get different codons?
Look up UUU on the chart and name the amino acid; then say what UAA does. (Answer: UUU = Phenylalanine; UAA = stop, which ends the protein.)