Question

The base that is not present in DNA is ________.

• A. uracil
• B. adenine
• C. guanine
• D. thymine
• E. cytosine

Hint:

DNA: ATGC; RNA: AUGC.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
This question tests fundamental knowledge about the chemical composition of nucleic acids, specifically Deoxyribonucleic Acid (DNA). DNA is a polymer made of repeating nucleotide units. Each nucleotide contains a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases.
Step 2: Detailed Explanation
The nitrogenous bases in nucleic acids are classified into two groups: purines and pyrimidines.
- The purines are Adenine (A) and Guanine (G). - The pyrimidines are Cytosine (C), Thymine (T), and Uracil (U). The composition of these bases is a key distinction between DNA and RNA (Ribonucleic Acid).
- In DNA, the four bases that are present are Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). - In RNA, the base Thymine is replaced by Uracil (U). So, the four bases in RNA are Adenine (A), Guanine (G), Cytosine (C), and Uracil (U). The question asks which base is not found in DNA. Based on the composition described above, Uracil is the base present in RNA but absent from DNA.
Step 4: Final Answer
The base that is not present in DNA is uracil.