Which of the following nitrogenous bases are found in both DNA and RNA?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Adenine and guanine
Nitrogenous bases are of two types: purines (adenine and guanine) and pyrimidines (cytosine, uracil and thymine). Thymine is found only in DNA, and in RNA it is replaced by uracil. Cytosine is common to both. So the bases found in both DNA and RNA are adenine, guanine and cytosine.
Option (1) Adenine and guanine — Correct. Adenine and guanine, the two purines, are present in both DNA and RNA.
Option (2) Guanine and uracil — Incorrect. Guanine is present in both, but uracil is found only in RNA, where it takes the place of thymine.
Option (3) Cytosine and thymine — Incorrect. Cytosine is common to both, but thymine is present only in DNA.
Option (4) Adenine and thymine — Incorrect. Adenine is present in both, but thymine is found only in DNA.
NCERT Extract:
Structure of Polynucleotide Chain – “… A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group. There are two types of nitrogenous bases – Purines (Adenine and Guanine), and Pyrimidines (Cytosine, Uracil and Thymine). Cytosine is common for both DNA and RNA and Thymine is present in DNA. Uracil is present in RNA at the place of Thymine.”