Mutation Lab

Change a DNA sequence. Follow the difference through codons to a growing protein.

Experimental human ribosome shown as grey protein cartoons and violet ribosomal RNA, with mint mRNA and pink transfer RNAs exposed in a cutaway.

Change one instruction

Predict whether the peptide will change, then translate both messages. Select any codon to link the DNA, RNA and amino acid.

Peptide so far · original: none yet · edited: none yet

A stylised ribosome reads mRNA 5′ → 3′. Letters on the growing chain are amino-acid symbols. Motion shows the order of events, not molecular geometry or speed. Swipe the diagram on a small screen.

Inspect the edited message

Base 6: T → C

Each tile shows coding DNA → mRNA → amino acid. Underlined tiles differ from the original. Swipe the strip on a small screen.

Codon 2: GCC specifies alanine.

GCU becomes GCC. Both codons specify alanine, so the amino-acid sequence stays the same. This alone does not establish that a variant has no biological effect.

Full peptide shown: MAEWPKG → MAEWPKG

Teaching scope: a synthetic coding sequence using the standard genetic code. Translation starts at the displayed AUG. This experiment does not predict folding, protein activity, RNA stability or disease effects.

Loading the experiment…

Quick reference

A message in triplets

During translation, a ribosome reads an mRNA in groups of three bases called codons. The reading frame determines where those groups start. Each sense codon specifies an amino acid; a stop codon signals termination.

Different edits, different consequences

A substitution may preserve the encoded amino acid, change it, or create a stop. An insertion or deletion within a coding region changes the downstream reading frame when its length is not a multiple of three.

Sequence is the beginning

A synonymous change leaves the amino-acid sequence unchanged, but can still affect other biological processes. A missense change does not establish whether a protein loses function. Experiments and additional evidence are needed.

Check your understanding Optional

A single base is deleted early in a coding sequence. Why can many later amino acids change?

Every later DNA base is replaced.The remaining bases are regrouped into different codons.The ribosome starts reading backwards.

At the bench

Use reading frames and translation to inspect your own sequence after practising on the teaching example.

Open Sequence

Sources and model notes

Structure-based views of resolved experimental coordinates. Cutaways, category colours, camera choices and guided highlights are authored for teaching. Coordinates remain fixed; highlights are not experimental trajectories or simulation outputs.

NHGRI · Frameshift mutation

How insertions and deletions alter a coding frame.

NCBI · The genetic codes

Codon assignments; this model uses the standard genetic code.