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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 ...
Base pairing: Two base pairs are produced by four nucleotide monomers, nucleobases are in blue. Guanine (G) is paired with cytosine (C) via three hydrogen bonds, in red. Adenine (A) is paired with uracil (U) via two hydrogen bonds, in red. Purine nucleobases are fused-ring molecules. Pyrimidine nucleobases are simple ring molecules.
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).
This enzyme would therefore recognize and cut out both types of uracil – the one incorporated naturally, and the one formed due to cytosine deamination, which would trigger unnecessary and inappropriate repair processes. [14] This problem is believed to have been solved in terms of evolution, that is by "tagging" (methylating) uracil.
A diagram of DNA base pairing, demonstrating the basis for Chargaff's rules. Chargaff's rules (given by Erwin Chargaff) state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine.
In the G-C Hoogsteen base pair, like the A-T Hoogsteen base pair, the purine (guanine) is rotated 180° about the glycosidic bond while the pyrimidine (cytosine) remains in place. One hydrogen bond from the Watson-Crick base pair is maintained (guanine O6 and cytosine N4) and the other occurs between guanine N7 and a protonated cytosine N3 ...
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]
CpG is shorthand for 5'—C—phosphate—G—3' , that is, cytosine and guanine separated by only one phosphate group; phosphate links any two nucleosides together in DNA. . The CpG notation is used to distinguish this single-stranded linear sequence from the CG base-pairing of cytosine and guanine for double-stranded sequenc