Gene to protein
A cell turns the code in a gene into a protein in two stages: transcription in the nucleus, then translation at a ribosome in the cytoplasm.
The gene in DNA
Inside the nucleus, DNA stores instructions as sequences of bases. A gene is the stretch that codes for one protein.
Transcription
RNA polymerase unzips the DNA at the gene and builds a matching strand of messenger RNA (mRNA), copying the code base by base.
Leaving the nucleus
The finished mRNA travels out through a nuclear pore into the cytoplasm, carrying the gene's message to the protein-making machinery.
The ribosome reads mRNA
A ribosome clamps onto the mRNA and reads it three bases at a time. Each three-base codon calls for one specific amino acid.
tRNAs deliver amino acids
Each tRNA has an anticodon that pairs with one codon and carries the matching amino acid. The ribosome links each new amino acid onto the chain.
The protein chain
Codon by codon, the chain grows until a stop codon is reached. The finished chain is released and folds into a working protein.