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Uracil (/ ˈ j ʊər ə s ɪ l /) (symbol U or Ura) is one of the four nucleotide bases in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine (T). Uracil is a demethylated form of thymine.
Wobble base pairs for inosine and guanine. A wobble base pair is a pairing between two nucleotides in RNA molecules that does not follow Watson-Crick base pair rules. [1] The four main wobble base pairs are guanine-uracil (G-U), hypoxanthine-uracil (I-U), hypoxanthine-adenine (I-A), and hypoxanthine-cytosine (I-C).
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.
Similarly, the simple-ring structure of cytosine, uracil, and thymine is derived of pyrimidine, so those three bases are called the pyrimidine bases. [ 6 ] Each of the base pairs in a typical double- helix DNA comprises a purine and a pyrimidine: either an A paired with a T or a C paired with a G.
Cytosine, thymine, and uracil are pyrimidines, hence the glycosidic bonds form between their 1 nitrogen and the 1' -OH of the deoxyribose. For both the purine and pyrimidine bases, the phosphate group forms a bond with the deoxyribose sugar through an ester bond between one of its negatively charged oxygen groups and the 5' -OH of the sugar. [2]
Cytosine (/ ˈ s aɪ t ə ˌ s iː n,-ˌ z iː n,-ˌ s ɪ n / [2] [3]) (symbol C or Cyt) is one of the four nucleotide bases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group ...
The bases form hydrogen bonds between cytosine and guanine, between adenine and uracil and between guanine and uracil. [2] However, other interactions are possible, such as a group of adenine bases binding to each other in a bulge, [ 3 ] or the GNRA tetraloop that has a guanine–adenine base-pair.
In animals it predominantly involves the addition of a methyl group to the carbon-5 position of cytosine residues of the dinucleotide CpG, and is implicated in repression of transcriptional activity. Treatment of DNA with bisulfite converts cytosine residues to uracil, but leaves 5-methylcytosine residues unaffected. Therefore, DNA that has ...