Why DNA is Better Genetic Material — NEET Biology
📚 Practice ConceptThe genetic material should be stable enough not to change with different stages of life cycle, age or with change in physiology of the organism. Stability as one of the properties of genetic material was very evident in Griffith's 'transforming principle' itself that heat, which killed the bacteria, at least did not destroy some of the properties of genetic material. This now can easily be explained in light of the DNA that the two strands being complementary if separated by heating come together, when appropriate conditions are provided. Further, 2'-OH group present at every nucleotide in RNA is a reactive group and makes RNA labile and easily degradable. RNA is also now known to be catalytic, hence reactive. Therefore, DNA chemically is less reactive and structurally more stable when compared to RNA. Therefore, among the two nucleic acids, the DNA is a better genetic material.
Which of the above statements concerning the nitrogenous bases and their properties in nucleic acids are NOT correct? S1: Purines, such as Adenine and Guanine, are double-ring structures found in both DNA and RNA. S2: Uracil is a pyrimidine nitrogenous base exclusively found in DNA, replacing Thymine. S3: In a DNA double helix, Adenine always forms two hydrogen bonds with Cytosine. S4: A nucleoside is formed when a nitrogenous base is linked to a pentose sugar through a N-glycosidic linkage. S5: The absence of a 2'-OH group in deoxyribose sugar contributes to DNA being chemically less reactive and structurally more stable than RNA.
View solution & NCERT explanation
Correct answer: B — S2 and S3 only
Let's evaluate each statement: S1: Correct. Purines, including Adenine and Guanine, are indeed double-ring nitrogenous bases and are common to both DNA and RNA. S2: Incorrect. Uracil is a pyrimidine found exclusively in RNA, where it replaces Thymine. Thymine is the pyrimidine found in DNA. S3: Incorrect. In a DNA double helix, Adenine always forms two hydrogen bonds with Thymine (A-T pairing). Guanine forms three hydrogen bonds with Cytosine (G-C pairing). S4: Correct. A nucleoside is correctly defined as a nitrogenous base linked to the 1' carbon of a pentose sugar (ribose or deoxyribose) via an N-glycosidic linkage. S5: Correct. The deoxyribose sugar in DNA lacks a hydroxyl (-OH) group at the 2'-position, which is present in the ribose sugar of RNA. This absence makes DNA chemically less reactive and structurally more stable than RNA, as the 2'-OH group in RNA makes it more labile and easily degradable. Therefore, statements S2 and S3 are NOT correct. This question tests the fundamental knowledge of nitrogenous bases, their classification, base pairing rules, and the key chemical differences between DNA and RNA that affect their stability.
What does NCERT say about genetic material should be?
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.