Protein synthesis: transcription and translation

Protein synthesis: transcription and translationSpec 3.8B

Protein synthesis has two main stages. In transcription, a copy of the gene is made as a strand of mRNA. In translation, the mRNA is used to build a polypeptide at a ribosome.

Transcription (in the nucleus)

1. RNA polymerase binds to the non-coding DNA located in front of a gene.
2. RNA polymerase produces a complementary mRNA strand from the coding DNA of the gene.
3. The mRNA moves out of the nucleus into the cytoplasm.

Translation (at a ribosome)

1. The mRNA attaches to a ribosome.
2. The mRNA is read in triplets of bases called codons. Each codon codes for a specific amino acid.
3. tRNA molecules transfer amino acids to the ribosome. Each tRNA carries the amino acid that matches a codon on the mRNA.
4. The amino acids are linked together to form a polypeptide, which folds into a protein.

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