What is DNA?

Someone ask: What is DNA?

DNA is long molecule in cells that carry building plan for body, like giant scroll wrapped tight in every tiny hut. It made of four chemical letters, and order of those letters tells cell how to make proteins, which do jobs like build muscle, carry oxygen, and run signals. DNA copied when cell divide, so offspring get family traits from parent tribe. Not every part of DNA make protein; some parts act like switch stones, telling when and where genes turn on. If DNA change, traits can change too. Caveman think of DNA like sacred carving on bone that guide how body grow and work. Cave wisdom: DNA is not body itself, but instruction fire that shapes body from inside.