Purines and Pyrimidines: Difference between revisions
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[[Purines|Purines]] and [[Pyrimidines|pyrimidines]] are the two | [[Purines|Purines]] and [[Pyrimidines|pyrimidines]] are the two distinct [[Nitrogenous base|nitrogenous]] nucleotide bases which form the five nucleobases present in [[DNA|DNA]] and [[RNA|RNA]]<ref name="[1]">Berg JM, Tymoczko JL, Gatto GJ Jr, Stryer L. Biochemistry. W. H. Freeman; 2015.</ref>. Pyrimidine bases are [[Heterocyclic|heterocyclic]] compounds which consist of a single carbon ring containing two nitrogen atoms, whereas purine bases consist of two carbon rings (a pyrimidine ring fused to an [[Imidazole|imidazole]] ring) containing a greater number of nitrogen atoms, so their structures provide distinct differences splitting nucleobases into two types. There are two types of Purines: [[Adenine|Adenine]] and [[Guanine|Guanine]], and three types of Pyrimidines: [[Cytosine|Cytosine]], [[Thymine|Thymine]] (which is only used in DNA, as its substituted by Uracil in RNA during [[DNA transcription|transcription]]) and [[Uracil|Uracil]] (which is only present in types of [[RNA Polymerase II|RNA]], such as [[MRNA|mRNA]] and [[TRNA|tRNA]] substituting Thymine)<ref name="[2]">Alberts B, Johnson A, Lewis J, Morgan D, Raff M, Roberts K, et al. Molecular Biology of the Cell. Garland Publishing; 2014.</ref>. | ||
=== Base pairing === | |||
Purines always bond with pyrimidines via [[Hydrogen bonds|hydrogen bonds]] following the [[Chargaff's Rules|Chargaff rule]] in [[DsDNA|dsDNA]], more specifically each bond follows [[Watson-Crick base pairing|Watson-Crick base pairing]] rules<ref name="[3]">Griffiths AJF, Miller JH, Suzuki DT, Lewontin RC, Gelbart WM. Structure of DNA. 2000 [cited 2017 Dec 6]; Available from: https://www.ncbi.nlm.nih.gov/books/NBK21786/</ref>. Therefore adenine specifically bonds to thymine forming two hydrogen bonds, whereas guanine forms three [[Hydrogen bonds|hydrogen bonds]] with Cytosine. During transcription and [[Translation|translation]] as thymine is substituted by uracil in RNA (mRNA and tRNA), uracil forms two hydrogen bonds with adenine so the pyrimidine-purine base pairing is maintained. | |||
=== References === | |||
<references /> | |||
Latest revision as of 09:52, 6 December 2017
Purines and pyrimidines are the two distinct nitrogenous nucleotide bases which form the five nucleobases present in DNA and RNA[1]. Pyrimidine bases are heterocyclic compounds which consist of a single carbon ring containing two nitrogen atoms, whereas purine bases consist of two carbon rings (a pyrimidine ring fused to an imidazole ring) containing a greater number of nitrogen atoms, so their structures provide distinct differences splitting nucleobases into two types. There are two types of Purines: Adenine and Guanine, and three types of Pyrimidines: Cytosine, Thymine (which is only used in DNA, as its substituted by Uracil in RNA during transcription) and Uracil (which is only present in types of RNA, such as mRNA and tRNA substituting Thymine)[2].
Base pairing
Purines always bond with pyrimidines via hydrogen bonds following the Chargaff rule in dsDNA, more specifically each bond follows Watson-Crick base pairing rules[3]. Therefore adenine specifically bonds to thymine forming two hydrogen bonds, whereas guanine forms three hydrogen bonds with Cytosine. During transcription and translation as thymine is substituted by uracil in RNA (mRNA and tRNA), uracil forms two hydrogen bonds with adenine so the pyrimidine-purine base pairing is maintained.
References
- ↑ Berg JM, Tymoczko JL, Gatto GJ Jr, Stryer L. Biochemistry. W. H. Freeman; 2015.
- ↑ Alberts B, Johnson A, Lewis J, Morgan D, Raff M, Roberts K, et al. Molecular Biology of the Cell. Garland Publishing; 2014.
- ↑ Griffiths AJF, Miller JH, Suzuki DT, Lewontin RC, Gelbart WM. Structure of DNA. 2000 [cited 2017 Dec 6]; Available from: https://www.ncbi.nlm.nih.gov/books/NBK21786/