Question

Which among the following is a double ring containing nitrogen base present in nucleic acids?

• A. Thymine
• B. Adenine
• C. Cytosine
• D. Uracil

Hint:

Use the mnemonic "PURE As Gold" to easily remember that Purines are Adenine and Guanine. Since the word "purine" is shorter than "pyrimidine", it counterintuitively corresponds to the larger, heavier double-ring structure!

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify the nitrogenous base found in nucleic acids (DNA/RNA) that possesses a double-ring chemical structure.

Step 2: Key Formula or Approach:
Nitrogenous bases in nucleic acids are broadly categorized into two families: 1.

Purines: Dual-ring structures consisting of a six-membered ring fused to a five-membered ring. 2.

Pyrimidines: Single-ring structures consisting of a solitary six-membered heterocyclic ring.

Step 3: Detailed Explanation:
Let's classify each of the given options based on their molecular framework:

Adenine (A) and

Guanine (G) are derivatives of purine, which means they are characterized by a fused

double-ring system containing nitrogen atoms.

Thymine (T),

Cytosine (C), and

Uracil (U) are derivatives of pyrimidine, which means they possess only a

single ring structure. Therefore, among the choices provided, Adenine is the only double-ring nitrogenous base.

Step 4: Final Answer:
The double-ring containing nitrogen base is Adenine, which corresponds to option (B).