Origin of First Genetic Material — NEET Biology
📚 Practice ConceptFrom foregoing discussion, an immediate question becomes evident – which is the first genetic material? It shall be discussed in detail in the chapter on chemical evolution, but briefly, we shall highlight some of the facts and points.
Which of the following statements regarding RNA's properties and its evolutionary significance are NOT correct? S1: The presence of a 2'-OH group in every nucleotide residue of RNA contributes to its enhanced chemical stability and reduced reactivity compared to DNA. S2: Ribozymes, which are RNA molecules with catalytic properties, provide crucial evidence supporting the hypothesis that essential life processes evolved around RNA. S3: DNA is primarily favored for the storage of genetic information due to its single-stranded nature and the presence of uracil, which facilitates rapid mutation. S4: The instability of RNA due to its reactive 2'-OH group and catalytic nature was a key factor that favored the evolution of more stable DNA as the predominant genetic material. S5: While RNA can function as genetic material in some viruses, its additional roles in most organisms are limited to acting solely as a messenger molecule. S6: Viruses with RNA genomes typically exhibit lower mutation rates and slower evolutionary adaptation compared to those with DNA genomes, attributing to RNA's inherent stability.
View solution & NCERT explanation
Correct answer: A — S1, S3, S5 and S6 are not correct
The core concept tested is the properties of RNA, its stability, catalytic function, and its role in the RNA world hypothesis compared to DNA. Let's evaluate each statement: S1: The presence of a 2'-OH group in every nucleotide residue of RNA makes it chemically *more* reactive and *less* stable than DNA. Therefore, this statement is NOT correct. S2: Ribozymes (RNA molecules acting as catalysts) are indeed strong evidence for RNA's primordial role in life processes, as mentioned in the NCERT text. This statement is correct. S3: DNA is favored for genetic information storage due to its *double-stranded* nature, *absence of a reactive 2'-OH group*, and the presence of *thymine* (not uracil), which contributes to its chemical stability and allows for repair mechanisms, thus resisting rapid mutation. Therefore, this statement is NOT correct. S4: RNA's instability and catalytic nature were indeed key drivers for the evolution of more stable DNA. This statement is correct. S5: RNA has additional roles beyond just being a messenger; it also functions as an adapter (tRNA), structural (rRNA), and catalytic molecule. Therefore, stating it acts 'solely as a messenger molecule' is NOT correct. S6: RNA being unstable, mutates at a faster rate. Consequently, viruses having RNA genomes and shorter life spans mutate and evolve faster. Therefore, this statement is NOT correct. Thus, statements S1, S3, S5, and S6 are NOT correct. Incorrect options: B. States S2 and S4 are not correct, but they are correct. C. Excludes S6 which is also not correct. D. Incorrectly claims S1, S3, S5, and S6 are correct. The final answer is A, as S1, S3, S5 and S6 are not correct. Recap: RNA is chemically less stable and more reactive than DNA due to its 2'-OH group, which also contributes to its catalytic activity (ribozymes). DNA, with its double-stranded structure, thymine, and lack of 2'-OH, is more stable and better suited for genetic information storage, having evolved from RNA.
What does NCERT say about From foregoing discussion immediate?
Has this concept appeared in NEET?
Which chapter is this from?
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