Start this worksheet with supplied mRNA. Keep its direction and reading frame visible; do not ask a model to infer an unidentified DNA strand or manufacture missing bases.
An original three-codon teaching sequence
Toy sequence for practice: 5′-AUG GCU UAA-3′, standard genetic code 1. It is not an identified natural protein or experimental sequence. The two-residue illustrative peptide is not a claim about biological function.
| Step | mRNA codon | Code result | Peptide record / action |
|---|---|---|---|
| 1 | AUG | Methionine, Met | Add Met. |
| 2 | GCU | Alanine, Ala | Add Ala: Met-Ala. |
| 3 | UAA | Stop | Terminate; retain Met-Ala. Do not add an amino acid. |
The NCBI standard-code table uses T rather than U in its displayed base alphabet. For these mRNA lookups, AUG corresponds to ATG, GCU to GCT, and UAA to TAA. Keep the mRNA itself written with U; the table convention does not turn it into DNA.
Make the reading frame part of the question
Number the bases 1 through 9. In the declared frame, read positions 1-3, 4-6, and 7-9 in the shown 5′ to 3′ direction. A next-step control should advance by three bases, not one.
For an extension, compare grouping from base 2: UGG | CUU | AA. The last group has only two bases and must remain incomplete. This grouping demonstration is not a claim that biological translation would initiate at base 2. Do not invent a third base to finish it.
Ask the learner to name the frame before choosing a table entry. A correct lookup from the wrong group does not answer the original question. Feedback should identify the selected positions and codon so that difference is visible.
Separate lookup, addition, and stopping
At AUG, ask which code-table result applies; at GCU, ask what is added next. At UAA, change the question to “What happens now?” The answer is termination, with the peptide trace unchanged.
Once the stop step is reached, another Next action must not add an invented amino acid. Reset should restore the declared frame, current codon, empty peptide trace, and unanswered state together. A reading exercise can demonstrate these transitions locally without collecting learner responses.
Reject invalid mRNA characters or incomplete triplets under the declared input contract. Preserve the rejected input with an explanation rather than silently changing it into a valid sequence. The teacher can supply a correction if that is the intended next task.
Copy a sequence-specific worksheet brief
Prepare an original protein-synthesis practice worksheet in US English.
Learner context: [enter or TO CONFIRM]
Supplied mRNA with direction and declared frame: [paste]
Genetic code table and identifier: [enter primary URL and code number]
Reviewed codon-to-result key: [paste]
Purpose of any alternate-frame comparison: [enter]
Show base positions, current triplet, table result, and peptide trace. Advance
by three bases in the declared frame. Distinguish adding an amino acid from
termination; stop is not an amino acid. Flag invalid characters/incomplete
triplets, never invent bases. Explain any table T/U convention without changing
the supplied mRNA. Label toy sequences and do not claim natural function,
gene editing, disease prediction, or transcription of an unknown DNA strand.
Return original items, lookup key and reasoning feedback. If requested,
provide HTML local practice with keyboard controls, stepping and reset.
Stop disables further additions; reset restores frame, codon and trace.
No response collection, specimen analysis, or copied simulation interface.
Check the sequence and stop step with a teacher before using the worksheet. NOS can save and display an HTML codon-review copy with the table result beside the peptide trace. Leave the class with the distinction intact: a codon can direct addition, or it can direct stopping; this sequence ends with two residues.