Deoxyribonucleic acid (DNA) contains the genetic instructions that determine an organism's traits. DNA has a double helix structure with a backbone made of alternating sugar and phosphate molecules, and bases (adenine, thymine, guanine, cytosine) that form rungs of the ladder-like structure. Genes are segments of DNA that code for proteins. Rosalind Franklin and Maurice Wilkins discovered that DNA has a helical structure using X-ray crystallography. James Watson and Francis Crick combined this evidence with their own research to establish DNA's double helix structure in 1953. DNA codes for amino acids that join to form proteins, which determine traits like eye and skin color. Gregor