The DNA template strand reads 3'-TACGGATCC-5'. Write the corresponding mRNA sequence.

MRNA is complementary to the template strand, with U replacing T. Read 5'→3': AUG CCU AGG.

How many amino acids are encoded by the mRNA: 5'-AUGGCCUAAUAG-3'?

AUG=start(Met), GCC=Ala, UAA=stop. So only 2 amino acids are incorporated (Met-Ala).

A mutation changes the 4th codon from GGG (Gly) to GGA. Is this a missense, nonsense, or silent mutation?

GGG and GGA both code for Glycine — this is a silent (synonymous) mutation.

A frameshift mutation inserts one nucleotide after position 3 of an mRNA. How many codons downstream are altered?

A frameshift shifts all downstream codons. Every codon from position 2 onwards is misread — all downstream amino acids change.

Pro 🔒~18 min

Protein Synthesis: Transcription & Translation

From DNA code to functional protein

How it works

Protein Synthesis: Transcription & Translation demonstrates a key principle: The Central Dogma describes the flow of genetic information. The Central Dogma describes the flow of genetic information. During transcription, RNA polymerase reads the template DNA strand (3'→5') and synthesizes a complementary mRNA strand (5'→3'), replacing T with U. The mRNA is then processed (5' cap, poly-A tail, intron splicing) before export from the nucleus. During translation, ribosomes read mRNA codons (3-nucleotide sequences) and tRNA molecules deliver the matching amino acids. The ribosome has three sites: A (aminoacyl), P (peptidyl), and E (exit). The polypeptide chain grows until a stop codon (UAA, UAG, UGA) is encountered, releasing the finished protein.

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Step-by-step

Press Play to watch transcription: RNA polymerase moves along the DNA template strand building mRNA.
When transcription completes, translation begins automatically — watch tRNA molecules deliver amino acids to the growing chain.
Click any codon on the mRNA to see which amino acid it encodes.
Use the speed controls to slow down and study each step.

Key formulas

$\text{DNA} \xrightarrow{\text{Transcription}} \text{mRNA} \xrightarrow{\text{Translation}} \text{Protein}$ The Central Dogma of Molecular Biology
$4^3 = 64 \text{ codons} \to 20 \text{ amino acids}$ 64 possible codons encode 20 amino acids (degenerate code)
$\text{Start: AUG (Met)} \quad \text{Stop: UAA, UAG, UGA}$ Universal start and stop codons

Frequently asked questions

The DNA template strand reads 3'-TACGGATCC-5'. Write the corresponding mRNA sequence.: MRNA is complementary to the template strand, with U replacing T. Read 5'→3': AUG CCU AGG.
How many amino acids are encoded by the mRNA: 5'-AUGGCCUAAUAG-3'?: AUG=start(Met), GCC=Ala, UAA=stop. So only 2 amino acids are incorporated (Met-Ala).
A mutation changes the 4th codon from GGG (Gly) to GGA. Is this a missense, nonsense, or silent mutation?: GGG and GGA both code for Glycine — this is a silent (synonymous) mutation.
A frameshift mutation inserts one nucleotide after position 3 of an mRNA. How many codons downstream are altered?: A frameshift shifts all downstream codons. Every codon from position 2 onwards is misread — all downstream amino acids change.