| DNA: The Cell's Life Pattern Deoxyribonucleic acid, or DNA, acts as a code for the cell's life pattern. Its structure is customarily illustrated in two forms-actual molecular structure and a diagrammatic representation. Within each molecule, two interwoven, twisted strands, shown here in gray, are held together by cross-linkages, shown in red, to form a spiral ladder-the double helix. The diagram shows first that each strand is composed of alternating deoxyribose sugar, shown in orange, and phosphate molecules, represented in purple. Attached to each sugar are molecules called bases, of which there are only four types found in DNA (here designated as red, blue, green or yellow). The pairing of specific bases (red with yellow, blue with green) forms the "rungs" of the ladder. The DNA code consists of a sequence of triplets of bases on one strand. Each triplet codes for an amino acid, and during protein synthesis amino acids are joined together. Any change in the sequence of triplets changes the protein that is produced. As all chemical reactions within cells are controlled by the action of a group of proteins-the enzymes-the DNA code regulates cell activity. |