Protein synthesis: transcription and translation

The central dogma in practice: how the information in DNA ends up as a protein, step by step, with codons and tRNA.

Direct answer: Protein synthesis follows the central dogma: DNA → mRNA → protein. In transcription (in the nucleus) RNA polymerase copies DNA into messenger RNA. In translation (at the ribosomes) the mRNA is read in codons and tRNA brings the amino acids that form the protein.

The two stages

	Transcription	Translation
Where	Nucleus	Ribosome (cytoplasm)
What it produces	Messenger RNA (mRNA)	Protein (chain of amino acids)
Key enzyme/actor	RNA polymerase	Ribosome + tRNA

Codon and anticodon

The mRNA is read in codons (groups of 3 nucleotides). Each codon corresponds to an amino acid. The tRNA has a complementary anticodon and brings the correct amino acid. The start codon is AUG (methionine).

Exam trap: do not confuse the codon (on the mRNA) with the anticodon (on the tRNA). A codon is 3 nucleotides = 1 amino acid, not 1 nucleotide.

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Frequently asked questions

What is the central dogma of biology?

The flow of genetic information: DNA → mRNA → protein.

Where do transcription and translation occur?

Transcription in the nucleus; translation at the ribosomes in the cytoplasm.

What is a codon?

A group of 3 mRNA nucleotides that codes for one amino acid.