Q.8 The information contained in DNA is used to synthesize proteins that are necessary
for the functioning of life. DNA is composed of four nucleotides: Adenine (A),
Thymine (T), Cytosine (C), and Guanine (G). The information contained in DNA
can then be thought of as a sequence of these four nucleotides: A, T, C, and G. DNA
has coding and non–coding regions. Coding regions—where the sequence of these
nucleotides are read in groups of three to produce individual amino
acids—constitute only about 2% of human DNA. For example, the triplet of
nucleotides CCG codes for the amino acid glycine, while the triplet GGA codes for
the amino acid proline. Multiple amino acids are then assembled to form a protein.
Based only on the information provided above, which of the following statements
can be logically inferred with certainty?
(i) The majority of human DNA has no role in the synthesis of proteins.
(ii) The function of about 98% of human DNA is not understood.
(A) only (i)
(B) only (ii)
(C) both (i) and (ii)
(D) neither (i) nor (ii)

The passage states that coding regions, read in groups of three nucleotides to produce amino acids for protein synthesis, constitute only about 2% of human DNA. This directly implies that the majority (98%) is non-coding and thus has no role in synthesizing proteins, making statement (i) certain. Statement (ii) cannot be inferred, as the passage provides no information about whether the function of non-coding DNA is understood or not—it only describes what coding regions do.​

Passage Analysis

The key detail is “Coding regions… constitute only about 2% of human DNA.” Non-coding regions are mentioned but not defined by function beyond this contrast. Logical inferences must stick strictly to provided facts, typical for CSIR NET-style questions on DNA structure and gene expression.​

Option Breakdown

• (i) The majority of human DNA has no role in the synthesis of proteins: True. Since coding regions (protein-coding) are 2%, the rest (98%) does not code for amino acids or proteins, per the description of triplet reading.​

• (ii) The function of about 98% of human DNA is not understood: False. The passage does not discuss if non-coding DNA’s function is known, unknown, or regulatory—it only contrasts coding vs. non-coding based on protein synthesis.​

• (A) only (i): Correct, as (i) follows directly while (ii) assumes extra knowledge.

• (B) only (ii): Incorrect—no basis for “not understood.”

• (C) both: Incorrect—(ii) overreaches.

• (D) neither: Incorrect—(i) is valid.​

Human DNA coding regions make up just 2% of the genome, where nucleotide triplets like CCG (glycine) and GGA (proline) direct protein synthesis essential for life. This CSIR NET Life Sciences question tests logical inference from DNA structure: coding regions are read in groups of three for amino acids, while the majority is non-coding. Understanding coding vs non-coding DNA is key for exams like CSIR NET, focusing on molecular biology basics without external assumptions.​

Why Only 2% Codes for Proteins?

Protein-coding genes occupy ~1-2% of human DNA, confirmed by genome projects—the rest includes introns, regulatory elements, and repeats. The passage limits inference to “no role in synthesis” for non-coding parts, not their full function.​

CSIR NET Inference Tips

• Stick to given info: Here, 98% non-coding means no direct protein role (i correct).

• Avoid extras: “Function not understood” (ii) needs proof beyond passage.
  Such questions appear in Unit 2 (Genetic Code, Genome Organization).​