Question

DNA and RNA contain the following two major purine bases:

• A. Guanine and cytosine
• B. Adenine and guanine
• C. Thymine and uracil
• D. Adenine and uracil

Answer 1

The Correct Option is C

The question asks about the two major purine bases found in DNA and RNA. To answer this question correctly, we need to understand what purines are.

Pyrimidines and Purines: In nucleic acids (DNA and RNA), the bases are categorized into two types: purines and pyrimidines. Purines contain a two-ring structure, while pyrimidines contain a single-ring structure.

Main Purines in Nucleic Acids:

• Adenine (A) - Found in both DNA and RNA.
• Guanine (G) - Found in both DNA and RNA.

Key Concepts:

DNA contains four nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). RNA also contains four bases, but instead of Thymine, it contains Uracil (U). Therefore, while Thymine is found in DNA, Uracil is found in RNA. The purines, Adenine and Guanine, are common to both DNA and RNA.

Given the options:

• Guanine and cytosine - Guanine is a purine, but cytosine is a pyrimidine.
• Adenine and guanine - Both adenine and guanine are purines and are found in both DNA and RNA. This is the correct answer.
• Thymine and uracil - Both are pyrimidines; thymine is found in DNA, and uracil is found in RNA.
• Adenine and uracil - Adenine is a purine, but uracil is a pyrimidine and found only in RNA.

The correct answer is therefore: Adenine and guanine.

Conclusion: Adenine and guanine are the two major purine bases present in both DNA and RNA. Understanding the structure and classification of nucleic acid bases is fundamental to answering this question.