Isolation of DNA — Prelims Strategy

Prelims Strategy

To excel in NEET questions on DNA isolation, a multi-pronged strategy is essential. Firstly, memorize the sequence of steps: Lysis $ightarrow$ Protein/RNA removal $ightarrow$ DNA precipitation $ightarrow$ Washing $ightarrow$ Rehydration.

This sequential understanding is frequently tested. Secondly, understand the specific function of each reagent. For example, know that detergents (SDS) lyse cells and denature proteins, Proteinase K digests proteins and inactivates nucleases, RNase degrades RNA, chilled ethanol/isopropanol precipitates DNA, and salts (sodium acetate) neutralize DNA charge to aid precipitation.

Pay special attention to enzymes used for different cell walls (e.g., cellulase for plants, lysozyme for bacteria). Thirdly, focus on the 'why' behind each step. Why is cold alcohol used? Why is EDTA in the storage buffer?

This conceptual clarity helps in solving application-based questions and avoiding trap options. For numerical problems (though rare in this specific topic), ensure units are consistent. Practice identifying common misconceptions, such as confusing the roles of different enzymes or the order of operations.

Always read all options carefully before selecting the best answer, as distractors are often plausible but incorrect functions of other reagents.