Caption

DNA molecule. Computer model of part of a molecule of deoxyribonucleic acid (DNA). DNA contains the inherited instructions that produce a living organism. The DNA molecule is made of two strands of atoms twisted into a helical shape. Each strand consists of an outer sugar-phosphate backbone (yellow), from which nucleotide bases project (blue-red). The four types of base link in complementary pairs. Adenine links with thymine, and cytosine with guanine.