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Thymine (/ ˈ θ aɪ m ɪ n /) (symbol T or Thy) is one of the four nucleotide bases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase. In RNA, thymine is replaced by the nucleobase uracil.
The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Five nucleobases— adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U)—are called primary or canonical .
In the canonical Watson-Crick base pairing, adenine (A) forms a base pair with thymine (T) and guanine (G) forms one with cytosine (C) in DNA. In RNA, thymine is replaced by uracil (U). Alternate hydrogen bonding patterns, such as the wobble base pair and Hoogsteen base pair , also occur—particularly in RNA—giving rise to complex and ...
The chemical structure of DNA base-pairs . A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA and RNA.
The purine bases adenine and guanine and pyrimidine base cytosine occur in both DNA and RNA, while the pyrimidine bases thymine (in DNA) and uracil (in RNA) occur in just one. Adenine forms a base pair with thymine with two hydrogen bonds, while guanine pairs with cytosine with three hydrogen bonds.
A tetraloop is a four-base pairs hairpin RNA structure. There are three common families of tetraloop in ribosomal RNA: UNCG, GNRA, and CUUG (N is one of the four nucleotides and R is a purine). UNCG is the most stable tetraloop. [9] Pseudoknot is an RNA secondary structure first identified in turnip yellow mosaic virus. [10]
The double helical structures of DNA or RNA are generally known to have base pairs between complementary bases, Adenine:Thymine (Adenine:Uracil in RNA) or Guanine:Cytosine. They involve specific hydrogen bonding patterns corresponding to their respective Watson-Crick edges, and are considered as Canonical Base Pairs.
Thymine occurs only in DNA and uracil only in RNA. Using amino acids and protein synthesis, [2] the specific sequence in DNA of these nucleobase-pairs helps to keep and send coded instructions as genes. In RNA, base-pair sequencing helps to make new proteins that determine most chemical processes of all life forms.