Question

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)

Hint:

In "inference with certainty" questions, be extremely cautious of strong words like "all," "none," "always," or "no". The correct inference is often a more moderately worded statement. If the text doesn't mention something (like the state of scientific knowledge), you cannot infer anything about it.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This is a critical reasoning question that tests the ability to make logical inferences based strictly on a given text. We must determine if the statements can be concluded with certainty from the provided information, without making outside assumptions.
Step 3: Detailed Explanation:
Let's analyze the passage:
- DNA information is used to synthesize proteins.
- DNA has coding and non-coding regions.
- Coding regions are ~2% of human DNA.
- The specific role of coding regions is described: sequences of three nucleotides are read to produce amino acids, which form proteins.
- The remaining ~98% is non-coding. The passage does NOT describe the function of this part.
Now let's evaluate the statements:
(i) The majority of human DNA has no role in the synthesis of proteins.
The passage states that ~98% of DNA is "non-coding". It defines "coding" as being read to produce amino acids. However, this does not mean the non-coding regions have "no role" in protein synthesis. Non-coding DNA could have regulatory roles (e.g., controlling when and how much protein is synthesized), which is still a "role in the synthesis of proteins". The passage does not provide enough information to rule this out. Therefore, we cannot infer with certainty that this 98% has "no role". This statement is too strong.
(ii) The function of about 98% of human DNA is not understood.
The passage describes what the 2% coding region does, but it remains completely silent on whether the function of the 98% non-coding region is understood or not. Just because the function is not mentioned in this short text does not mean it is not understood by scientists. Making this conclusion would be an argument from ignorance. The passage provides no basis to make any claim about the state of scientific knowledge.
Conclusion:
Neither statement (i) nor statement (ii) can be inferred with certainty from the given text. Statement (i) makes too strong a claim ("no role"), and statement (ii) makes a claim about scientific knowledge that is not supported by the text.
Step 4: Final Answer:
Neither (i) nor (ii) can be logically inferred.
Step 5: Why This is Correct:
For an inference to be certain, it must be directly and unavoidably supported by the text. Both statements go beyond the information provided. The text limits its description of non-coding DNA's role without declaring it has 'no role' or is 'not understood'.