Which of the following is NOT a nitrogenous base in DNA?
Show answer & explanation
Correct answer: B
Explanation
Answer: Uracil.
Explanation —
DNA (Deoxyribonucleic Acid) contains four main nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). Uracil (U) is found only in RNA (Ribonucleic Acid), where it takes the place of Thymine. In the structure of DNA, Adenine always pairs with Thymine, and Cytosine always pairs with Guanine. The presence of Uracil is a key chemical characteristic that distinguishes RNA from DNA.
Additional Points —
Purines: Adenine and Guanine are classified as purines.
Pyrimidines: Cytosine, Thymine, and Uracil fall under the category of pyrimidines.
Potential Exam Questions and Answers
Question: Which base is found in RNA in place of Thymine?
Answer: Uracil.
Question: Who proposed the 'double-helix' structure of DNA?
Answer: Watson and Crick.