Question

The pyrimidine bases found in RNA are

• A. Thymine& Uracil
• B. Thymine& Cytosine
• C. Adenine& Guanine
• D. Uracil& Cytosine

Hint:

To easily remember the bases, think of them as: \textbf{DNA:} A, T, G, C (Adenine, Thymine, Guanine, Cytosine) \textbf{RNA:} A, U, G, C (Adenine, Uracil, Guanine, Cytosine) The only difference is that Thymine (T) in DNA is replaced by Uracil (U) in RNA. Pyrimidines are C, T, U. Purines are A, G.

Answer 1

The Correct Option is D

Step 1: Recall the Types of Nitrogenous Bases in Nucleic Acids
Nucleic acids (DNA and RNA) are composed of nucleotides, which consist of a nitrogenous base, a pentose sugar, and a phosphate group. The nitrogenous bases are classified into two main categories: \begin{itemize} \item Purines: These are larger bases with a double-ring structure. The purines found in both DNA and RNA are Adenine (A) and Guanine (G). \item Pyrimidines: These are smaller bases with a single-ring structure. The pyrimidines differ between DNA and RNA. \end{itemize} Step 2: Identify Pyrimidine Bases in DNA
In DNA (Deoxyribonucleic Acid), the pyrimidine bases are: \begin{itemize} \item Cytosine (C) \item Thymine (T) \end{itemize} Step 3: Identify Pyrimidine Bases in RNA
In RNA (Ribonucleic Acid), the pyrimidine bases are: \begin{itemize} \item Cytosine (C) \item Uracil (U) \end{itemize} Note that Uracil replaces Thymine in RNA. Step 4: Answer the Question Based on RNA Pyrimidines
The question asks for the pyrimidine bases found in RNA. Based on Step 3, these are Uracil and Cytosine. Step 5: Analyze Options
\begin{itemize} \item Option (1): Thymine& Uracil. Incorrect. Thymine is in DNA, Uracil is in RNA. They are not simultaneously found as the primary pyrimidines in a single type of nucleic acid (unless discussing precursors/metabolism). This option lists one from DNA and one from RNA. \item Option (2): Thymine& Cytosine. Incorrect. These are the pyrimidine bases found in DNA, not RNA. \item Option (3): Adenine& Guanine. Incorrect. These are purine bases, not pyrimidine bases. \item Option (4): Uracil& Cytosine. Correct, as these are the two pyrimidine bases characteristic of RNA. \end{itemize}