Search results
Results from the WOW.Com Content Network
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.
Pyrimidine (C 4 H 4 N 2; / p ɪ ˈ r ɪ. m ɪ ˌ d iː n, p aɪ ˈ r ɪ. m ɪ ˌ d iː n /) is an aromatic, heterocyclic, organic compound similar to pyridine (C 5 H 5 N). [3] One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring.
The 6–4 photoproduct (6–4 pyrimidine–pyrimidone, or 6–4 pyrimidine–pyrimidinone) is an alternate dimer configuration consisting of a single covalent bond linking the carbon at the 6 (C6) position of one pyrimidine ring and carbon at the 4 (C4) position of the adjoining base's ring. [11]
Pyrimidine degradation ultimately ends in the formation of ammonium, water, and carbon dioxide. The ammonium can then enter the urea cycle which occurs in the cytosol and the mitochondria of cells. [5] Pyrimidine bases can also be salvaged. For example, the uracil base can be combined with ribose-1-phosphate to create uridine monophosphate or UMP.
The nitrogenous bases are either purines or pyrimidines, heterocycles whose structures support the specific base-pairing interactions that allow nucleic acids to carry information. The base is always bonded to the 1'-carbon of the deoxyribose, an analog of ribose in which the hydroxyl group of the 2'-carbon is replaced with a hydrogen atom.
B-DNA is the most common form of DNA in vivo and is a more narrow, elongated helix than A-DNA. Its wide major groove makes it more accessible to proteins. On the other hand, it has a narrow minor groove. B-DNA's favored conformations occur at high water concentrations; the hydration of the minor groove appears to favor B-DNA.
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.
While canonical Watson-Crick base pairs are most prevalent and are commonly observed in a majority of chromosomal DNA and in most functional RNAs, presence of stable non-canonical base pairs is also extremely significant in DNA biology. An example of non-Watson-Crick, or non-canonical, base pairing can be found at the ends of chromosomal DNA.