Which of the following is a nitrogenous base found in RNA but not in DNA?
A) Adenine
B) Thymine
C) Uracil
D) Cytosine
The correct answer and explanation is:
The correct answer is C) Uracil.
Explanation:
RNA (Ribonucleic Acid) and DNA (Deoxyribonucleic Acid) are both nucleic acids that play essential roles in the storage and transmission of genetic information. They both consist of long chains of nucleotides, which are the basic building blocks of these molecules. A nucleotide consists of three components: a phosphate group, a sugar (ribose in RNA and deoxyribose in DNA), and a nitrogenous base.
There are five nitrogenous bases in total, which can be categorized into purines and pyrimidines:
- Purines: Adenine (A) and Guanine (G)
- Pyrimidines: Cytosine (C), Thymine (T), and Uracil (U)
DNA contains the bases Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). In contrast, RNA contains Adenine (A), Uracil (U), Cytosine (C), and Guanine (G). The key difference is that RNA has Uracil (U) instead of Thymine (T).
The substitution of Uracil for Thymine in RNA is significant because it reflects a difference in structure. Uracil is structurally simpler than Thymine, lacking a methyl group (-CH3) that Thymine has. This change helps distinguish RNA from DNA and plays a role in how the two molecules function in the cell.
When RNA is transcribed from DNA during protein synthesis, Adenine (A) in the DNA pairs with Uracil (U) in RNA instead of Thymine (T). This base pairing is crucial for the correct encoding of genetic information and protein synthesis.