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.
In both DNA and RNA, nitrogenous bases are crucial components of nucleotides, the building blocks of these nucleic acids. These bases are divided into purines (adenine, guanine) and pyrimidines (cytosine, thymine, uracil). While both DNA and RNA share adenine (A), guanine (G), and cytosine (C) as common bases, thymine (T) is exclusive to DNA, and uracil (U) is exclusive to RNA.
In DNA, thymine pairs with adenine to form a base pair through hydrogen bonds. This pairing is a key feature of the double-helix structure of DNA, helping it to store genetic information in a stable, long-term format. On the other hand, uracil, which is structurally similar to thymine but lacks a methyl group, is found in RNA. Instead of thymine, uracil pairs with adenine during the synthesis of RNA.
The presence of uracil in RNA and thymine in DNA is part of the reason why these two nucleic acids serve different functions in the cell. RNA is typically single-stranded and involved in protein synthesis and gene regulation, while DNA is double-stranded and stores genetic information for inheritance. Uracil in RNA is more reactive due to its lack of the methyl group, making RNA more prone to degradation compared to the more stable DNA.
Moreover, uracil’s role in RNA is essential for the proper transcription and translation processes. The presence of uracil allows RNA to be flexible and efficient in carrying out its various roles, from messenger RNA (mRNA) to transfer RNA (tRNA) and ribosomal RNA (rRNA), all of which are integral to protein production.