Protein Synthesis (3D)

Transcription and translation from DNA to functional protein

Protein synthesis has two stages. Transcription occurs in the nucleus: RNA polymerase reads the DNA template strand 3'→5' and synthesizes mRNA 5'→3', using complementary base pairing (A→U, T→A, G→C, C→G). The mRNA is processed (5' cap, poly-A tail, intron removal) and exported to the cytoplasm. Translation occurs at ribosomes: mRNA codons (3-nucleotide sequences) are read 5'→3'. Each codon is matched by a tRNA anticodon carrying the specified amino acid. Peptide bonds form between adjacent amino acids. Translation starts at AUG (methionine) and ends at a stop codon (UAA, UAG, UGA). Mutations can alter the protein: substitution may change one amino acid (missense) or create a stop (nonsense), while insertion/deletion causes a frameshift affecting all downstream amino acids.