Which of the following nucleotides is only found in RNA?
A.
Adenine
B.
Uracil
C.
Guanine
D.
Thymine
The Correct Answer and Explanation is:
The correct answer is B. Uracil.
Explanation:
Nucleotides are the building blocks of nucleic acids, which are essential macromolecules in all living organisms. The two primary types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Both DNA and RNA are composed of long chains of nucleotides, which consist of three components: a phosphate group, a five-carbon sugar, and a nitrogenous base.
The nitrogenous bases in DNA and RNA are categorized into two groups:
- Purines: Adenine (A) and Guanine (G).
- Pyrimidines: Cytosine (C), Thymine (T), and Uracil (U).
In DNA, the four nitrogenous bases are Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). These bases pair specifically: Adenine pairs with Thymine, and Guanine pairs with Cytosine. The sugar in DNA is deoxyribose.
In RNA, however, Thymine is not present. Instead, RNA contains Uracil (U) as a nitrogenous base, which replaces Thymine. The four nitrogenous bases in RNA are Adenine (A), Uracil (U), Guanine (G), and Cytosine (C). In RNA, Adenine pairs with Uracil. The sugar in RNA is ribose, which differs from deoxyribose by having one more oxygen atom.
The presence of Uracil is one of the key differences between RNA and DNA. This difference is crucial because it reflects the distinct roles of these nucleic acids. DNA serves as the long-term storage of genetic information, while RNA is primarily involved in protein synthesis and other cellular functions.
Uracil’s inclusion in RNA and absence in DNA plays a significant role in the structural and functional diversity of these nucleic acids. Uracil allows RNA to perform various tasks in the cell, including acting as a messenger (mRNA), a component of ribosomes (rRNA), and a transfer molecule during protein synthesis (tRNA). The specificity of these roles underlines the evolutionary importance of the distinction between DNA and RNA.