Question

Purines found both in DNA and RNA are:

• A. Adenine and thymine
• B. Adenine and guanine
• C. Guanine and cytosine
• D. Cytosine and thymine

Answer 1

The Correct Option is B

To determine which purines are found both in DNA and RNA, it is essential to understand the basic structure of nucleic acids and the types of nitrogenous bases found in them.

Nucleic Acids and Their Bases:

• Nucleic acids, such as DNA and RNA, are composed of nucleotides. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base.
• There are two types of nitrogenous bases: purines and pyrimidines.
• Purines are double-ring structures, while pyrimidines are single-ring structures.

Pyrimidines and Purines:

• Purines: Adenine (A) and Guanine (G)
• Pyrimidines: Cytosine (C), Thymine (T), and Uracil (U)

DNA vs. RNA:

• DNA: Contains Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).
• RNA: Contains Adenine (A), Uracil (U) (instead of Thymine), Guanine (G), and Cytosine (C).

From the above information, we can observe that both DNA and RNA share the purines Adenine (A) and Guanine (G).

Now, let's evaluate the given options:

1. Adenine and thymine: Thymine is a pyrimidine found in DNA but not in RNA.
2. Adenine and guanine: Both are purines found in both DNA and RNA.
3. Guanine and cytosine: Cytosine is a pyrimidine, not a purine.
4. Cytosine and thymine: Both are pyrimidines, not purines.

The correct answer is, therefore, Adenine and guanine, as these are the purines common to both DNA and RNA.