Question

How many of the nitrogen-containing bases are common among both DNA and RNA?

• A. Four
• B. Two
• C. Three
• D. One

Hint:

Adenine and cytosine are the two nitrogenous bases common to both DNA and RNA.

Answer 1

The Correct Option is B

Step 1: Understanding nitrogen-containing bases.
Both DNA and RNA share two nitrogenous bases: adenine (A) and cytosine (C). However, DNA contains thymine (T), while RNA contains uracil (U) instead.
Step 2: Analyzing the options.
(A) Four: Incorrect, there are four nitrogenous bases in each, but only two are common to both DNA and RNA.
(B) Two: Correct, adenine (A) and cytosine (C) are common to both DNA and RNA.
(C) Three: Incorrect, only two nitrogenous bases are common to both DNA and RNA.
(D) One: Incorrect, there are two common bases, not one.
Step 3: Conclusion.
The correct answer is (B) Two, as adenine and cytosine are common to both DNA and RNA.