The building blocks of DNA and RNA, known as nucleotides, are composed of a sugar, a phosphate group, and a crucial component called nitrogenous bases or nucleobases. These are nitrogen-containing compounds that play a significant role in the structure of our genetic material. The five main bases are Adenine (A), Cytosine (C), Guanine (G), Thymine (T) and Uracil (U).
Let's delve deeper into these five types of nucleotides.
Adenine, a purine-derived nucleobase, boasts a two-ringed structure with an amino group at the C6 position. It forms a covalent bond with the ribose or deoxyribose sugar and a hydrogen bond with either thymine or uracil in the nucleotide structure.
Adenine also plays a role in forming other compounds like vitamin B12, ATP, NAD, and FAD.
Guanine is another purine-derived nucleobase, characterized by a two-ringed structure formed by a fused pyrimidine-imidazole ring system. It pairs with cytosine in the nucleotide sequence, forming hydrogen bonds.
Guanine forms guanosine when combined with ribose, and deoxyguanosine when combined with deoxyribose.
Thymine, a member of the pyrimidine family, forms double hydrogen bonds with adenine in the DNA helix. Also referred to as 5-methyluracil, it is methylated at the C5 position in the molecule and is absent in RNA strands.
Cytosine, a pyrimidine-derived nitrogenous base, carries an amino group at the C4 position. It forms triple hydrogen bonds with guanine in the DNA helix.
Uracil, another pyrimidine-derived nitrogenous base, is exclusive to RNA molecules, replacing thymine. It is essentially a demethylated form of thymine, with oxo groups at C2 and C4.
- Adenine
- Guanine
- Thymine
- Cytosine
- Uracil
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Also Read:
- Differences between Nucleotide and Nucleoside
- Nucleotide MCQs for NEET 2022
- Understanding Nucleic Acid and Genetic Code – Structure and Functions