Watson-Crick Model — Prelims Strategy

Prelims Strategy

To excel in NEET questions on the Watson-Crick model, a multi-pronged strategy is essential. Firstly, memorize key facts and dimensions: the diameter (2 nm), pitch (3.4 nm), base pairs per turn (10 bp), and distance between adjacent base pairs (0.

34 nm). Secondly, master Chargaff's rules ($A=T$, $G=C$, and $A+G=T+C$) and practice numerical problems involving base percentages. Be careful with single-stranded vs. double-stranded DNA context.

Thirdly, understand the types of bonds: phosphodiester bonds (strong, within a strand), glycosidic bonds (sugar-base), and hydrogen bonds (weak, between strands, A-T has 2, G-C has 3). Fourthly, grasp conceptual implications: why antiparallelism is important, how complementary base pairing enables replication, and the significance of major/minor grooves.

For conceptual questions, carefully read each option, identifying keywords that might make a statement incorrect (e.g., 'three' hydrogen bonds for A-T). For numerical problems, write down the given information and the relevant formula (Chargaff's rules) before calculating.

Avoid common traps like confusing the number of hydrogen bonds or misinterpreting dimensions.