The chemical reactions and pathways resulting in the formation of tetracycline, (4S,4aS,5aS,6S,12aS)-4-(dimethylamino)-3,6,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-1,4,4a,5,5a,6,11,12a-octahydrotetracene-2-carboxamide, a broad-spectrum antibiotic produced by streptomyces bacteria that blocks binding of aminoacyl tRNA to the ribosomes of both Gram-positive and Gram-negative organisms (and those of organelles).