Which of the following nitrogen base is not seen in RNA:
**Core Concept**
The question is testing the student's knowledge of the nitrogenous bases found in RNA (Ribonucleic Acid). RNA is a single-stranded nucleic acid that serves as a messenger molecule in protein synthesis. The four nitrogenous bases found in RNA are adenine (A), guanine (G), cytosine (C), and uracil (U).
**Why the Correct Answer is Right**
The correct answer is **uridine** (which contains the nitrogen base uracil), but since the options are incomplete we will explain. Adenine, guanine, and cytosine are found in both DNA and RNA. However, RNA contains the nitrogen base uracil instead of thymine (T), which is found in DNA. This is due to the presence of the enzyme uracil-DNA glycosylase in cells, which removes uracil from DNA, thereby preventing its incorporation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is missing, but if it were a correct option, we would explain why it is incorrect below.
* **Option B:** This option is also missing, but if it were a correct option, we would explain why it is incorrect below.
* **Option C:** This option is missing, but if it were a correct option, we would explain why it is incorrect below.
* **Option D:** This option is missing, but if it were a correct option, we would explain why it is incorrect below.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that RNA contains the nitrogen base uracil instead of thymine, which is a key difference between RNA and DNA.
**Correct Answer:**
(Note: Since the options are incomplete, we cannot provide a correct answer.)