The correct answer is Option (1) → Uracil
The provided structure of the nucleic acid base is Uracil.
Key Structural Features of Uracil
Uracil ($C_4H_4N_2O_2$) is a pyrimidine base characterized by a single six-membered heterocyclic ring. Its identity is confirmed by the following functional groups:
- Two Carbonyl Groups: It has two oxo ($=O$) groups attached at the C2 and C4 positions of the ring.
- Lack of Methyl Group: Unlike its DNA counterpart, Thymine, uracil lacks a methyl group ($-CH_3$) at the C5 position.
- Nitrogen Atoms: The ring contains two nitrogen atoms at positions 1 and 3.
Biological Significance
- RNA Specificity: Uracil is found exclusively in RNA molecules, where it takes the place of thymine.
- Base Pairing: In RNA, uracil forms two hydrogen bonds with adenine.
- Demethylated Thymine: Chemically, uracil can be considered a demethylated form of thymine.
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