🧬 Transcription 🔗 Translation 📖 64 codons → 20 amino acids ⚡ Mutation explorer

Protein Synthesis Simulator

Q: What is a frameshift mutation?

An insertion or deletion whose length is not divisible by 3. It shifts the reading frame, so every downstream codon is re-grouped — usually producing a garbled sequence and often a premature stop codon.

Q: Why is the genetic code degenerate?

Most amino acids are encoded by multiple codons — leucine has six. Redundancy at the third (wobble) position buffers many point mutations into silent changes. Only methionine and tryptophan have a single codon.

Q: What is the difference between the template and coding strand?

The template (antisense) strand is the one actually read by RNA polymerase; the mRNA is complementary to it. The coding (sense) strand matches the mRNA sequence except it has T instead of U.

Type a DNA sequence and watch the central dogma run: transcription to mRNA, then translation to a protein — with start/stop codon logic and a mutation explorer for silent, missense, nonsense, and frameshift changes.

Quick Answer

Protein synthesis has two stages. Transcription copies a DNA template into mRNA (T → U). Translation reads mRNA in triplets (codons); AUG starts (Met), and UAA, UAG, UGA stop. The standard genetic code maps 64 codons to 20 amino acids plus stops.

Strand type

Coding strand matches the mRNA (T→U). Type it 5'→3'.

DNA sequence (A, T, G, C only)

Mutation explorer

Transcription, translation, and why sequence order matters

Both stages build their product 5'→3': RNA polymerase adds nucleotides to the 3' end of the growing mRNA, and the ribosome reads the mRNA from its 5' end toward 3'. That's why this simulator asks which strand you typed and in which direction — flipping a sequence or swapping strands changes the protein entirely.

Wobble pairing and degeneracy

The genetic code is degenerate: 64 codons, 20 amino acids. Most of the redundancy lives at the third codon position, where tRNA anticodons tolerate non-standard "wobble" pairing. Leucine and serine have six codons each; methionine and tryptophan have exactly one. This is evolution's error buffer — many third-position point mutations are silent, leaving the protein unchanged.

One letter, one disease: sickle cell

The classic missense example is sickle-cell anemia: a single substitution changes the β-globin codon GAG → GTG, swapping glutamate (Glu) for valine (Val) at position 6. One hydrophobic residue in place of a charged one is enough to make hemoglobin polymerize and deform red blood cells. A nonsense mutation (codon → stop) truncates the protein outright, and a frameshift — an insertion or deletion not divisible by 3 — re-groups every downstream codon, usually scrambling the chain and hitting a premature stop. Try each in the mutation explorer above.

The standard genetic code (all 64 codons)

Each block fixes the first nucleotide; rows are the second nucleotide, columns the third. AUG is the start codon; the three Stop entries terminate translation.

U__	_U	_C	_A	_G
_U_	UUU Phe	UUC Phe	UUA Leu	UUG Leu
_C_	UCU Ser	UCC Ser	UCA Ser	UCG Ser
_A_	UAU Tyr	UAC Tyr	UAA Stop	UAG Stop
_G_	UGU Cys	UGC Cys	UGA Stop	UGG Trp

C__	_U	_C	_A	_G
_U_	CUU Leu	CUC Leu	CUA Leu	CUG Leu
_C_	CCU Pro	CCC Pro	CCA Pro	CCG Pro
_A_	CAU His	CAC His	CAA Gln	CAG Gln
_G_	CGU Arg	CGC Arg	CGA Arg	CGG Arg

A__	_U	_C	_A	_G
_U_	AUU Ile	AUC Ile	AUA Ile	AUG Met
_C_	ACU Thr	ACC Thr	ACA Thr	ACG Thr
_A_	AAU Asn	AAC Asn	AAA Lys	AAG Lys
_G_	AGU Ser	AGC Ser	AGA Arg	AGG Arg

G__	_U	_C	_A	_G
_U_	GUU Val	GUC Val	GUA Val	GUG Val
_C_	GCU Ala	GCC Ala	GCA Ala	GCG Ala
_A_	GAU Asp	GAC Asp	GAA Glu	GAG Glu
_G_	GGU Gly	GGC Gly	GGA Gly	GGG Gly

Stage	In	Out	Machine	Key rule
Transcription	DNA template (3'→5')	pre-mRNA (5'→3')	RNA polymerase	Complementary base pairing; U replaces T
RNA processing	pre-mRNA	Mature mRNA	Spliceosome + enzymes	5' cap, poly-A tail, introns spliced out
Translation	mRNA codons	Polypeptide	Ribosome + tRNA	AUG starts; UAA/UAG/UGA stop; one codon → one amino acid

Mutation type	DNA change	Protein effect
Silent	Point substitution (often 3rd position)	None — degenerate code gives same amino acid
Missense	Point substitution	One amino acid swapped (sickle cell: GAG→GTG, Glu→Val)
Nonsense	Point substitution	Codon becomes a stop — truncated protein
Frameshift	Insertion/deletion not divisible by 3	Every downstream codon re-read; garbled chain, often early stop

Frequently Asked Questions

What is the central dogma?

Information flows DNA → RNA → protein. Transcription makes RNA from a DNA template; translation makes protein from the mRNA. Reverse transcription exists in retroviruses but is an exception.

What are the three stop codons?

UAA, UAG, and UGA. They don't encode amino acids; release factors terminate the chain. AUG is the start codon and encodes methionine.

What is a frameshift mutation?

An insertion or deletion not divisible by 3 that shifts the reading frame. Every downstream codon is re-grouped, usually producing a garbled sequence and often a premature stop.

Why is the genetic code degenerate?

Most amino acids have multiple codons (leucine has six). Redundancy at the third (wobble) position buffers many point mutations into silent changes. Only Met and Trp have a single codon.

What is the difference between the template and coding strand?

The template (antisense) strand is read by RNA polymerase; the mRNA is complementary to it. The coding (sense) strand matches the mRNA except T instead of U.

Related Calculators

Genetics Protein Intake BMI

Sources & Methodology

Transcription converts the entered strand to mRNA (coding: T→U; template: complement with U). Translation scans for the first AUG, maps each in-frame codon via the standard genetic code, and stops at the first UAA, UAG, or UGA.

Standards and figures reviewed 2026.