Target Exam

CUET

Subject

Biology

Chapter

Molecular Basis of Inheritance

Question:

Choose the most appropriate option about the presence of nitrogenous bases; Cytosine, 5-methyl uracil and Uracil.

Options:

Cytosine only in DNA, 5-Methyl Uracil in both; DNA and RNA, Uracil only in RNA

Cytosine only in RNA, 5-Methyl Uracil only in DNA, Uracil in both DNA and RNA

Cytosine in both; DNA and RNA, 5-Methyl Uracil only in DNA and Uracil only in RNA

Cytosine only in RNA 5-Methyl Uracil in both; DNA and RNA, Uracil only in DNA

Correct Answer:

Cytosine in both; DNA and RNA, 5-Methyl Uracil only in DNA and Uracil only in RNA

Explanation:

The correct answer is Option (3) → Cytosine in both; DNA and RNA, 5-Methyl Uracil only in DNA and Uracil only in RNA 

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 (5-methyl uracil, another chemical name for thymine). is present in DNA. Uracil is present in RNA at the place of Thymine.