Question

The information contained in DNA is used to synthesize proteins necessary for life. DNA is composed of four nucleotides: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). Coding regions—where nucleotide triplets code for amino acids—constitute only about 2% of human DNA. Based only on the information above, which of the following statements can be 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:

Be cautious: “does not code for proteins” $\neq$ “function not understood.” Only infer what is explicitly supported by the passage.

Answer 1

The Correct Option is A

Step 1: Re-read the passage facts.
- Coding regions (protein-coding sequences) are about 2% of human DNA.
- No statement is given about whether the other 98% has any understood or unknown function.
Step 2: Check statement (i).
If only 2% of DNA codes for proteins, then clearly the remaining 98% does not code for proteins. Hence, the majority (98%) has no role in direct protein synthesis. This is certainly true.
Step 3: Check statement (ii).
The passage does not say that the function of the remaining 98% is “not understood.” It only says it does not code for amino acids. It may have other known regulatory or structural roles. Therefore, we cannot conclude this with certainty.
Step 4: Conclude.
Only (i) can be inferred with certainty. Final Answer: \[ \boxed{\text{only (i)}} \]