Base pairing and the central dogma

The information flows DNA -> RNA -> protein (Crick's central dogma), and it is held by complementary pairs: A binds T with two hydrogen bonds, G binds C with three. Chargaff's rule (that A=T and G=C in any genome's counts) was the clue Watson and Crick needed. The engine verifies complements in-domain (https://narrowhighway.com/s/81e65a70a2e8e96d2e46f9d45523790c95ed9fe05ea8f89284b0d35845d11b27 ). That one extra bond on G-C is why GC-rich DNA melts at a higher temperature — an empirical, measured property that thermophiles exploit. The double helix is a two-strand error-correcting code: each strand is the other's backup.