UPPSC 2012 General Studies I Solved Paper

(a) Watson and Creek proposed for the first time the double helix model of DNA. A DNA molecule consists of two strands that wind around each other like a twisted ladder. Each strand has a backbone made of alternating groups of sugar(deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A),cytosine (C), guanine (G), or thymine (T).