Watson-Crick base pairing

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[[Image:Watson n crick.jpg|left|James Watson and Francis Crick]] [[Image:BASE PAIRS.png|right|199x253px|Figure 1.1 A-T and G-C base pairs]]  
 
[[Image:Watson n crick.jpg|left|James Watson and Francis Crick]] [[Image:BASE PAIRS.png|right|199x253px|Figure 1.1 A-T and G-C base pairs]]  
  
DNA consists of two types of bases namely; [[Purine|purines]] and [[Pyrimidine|pyrimidines]]. There are two types of purines: [[Adenine|adenine]] and [[Guanine|guanine]] as well as two types of Pyrimidines: [[Cytosine|cytosine]] and [[Thymine|thymine]]. In the Watson-Crick DNA base pairing model a purine always binds with a pyrimidine, however, each purine binds to one particular type of pyrimidine.  
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DNA consists of two types of bases, namely; [[Purine|purines]] and [[Pyrimidine|pyrimidines]]. There are two types of purines: [[Adenine|adenine]] and [[Guanine|guanine]], as well as two types of Pyrimidines: [[Cytosine|cytosine]] and [[Thymine|thymine]]. In the Watson-Crick DNA base pairing model a purine always binds with a pyrimidine, however, each purine binds to one particular type of pyrimidine.  
  
Adenine (A) binds to thymine (T) whilst, guanine (G) binds to cytosine (C); although in RNA&nbsp;unracil (U)&nbsp;is substituted for thymine (T). This base pairing is referred to as complementary, hence the base pairs are called complementary [[Base pairs|base pairs]]&nbsp;<ref>Hartl D., Ruvolo M. (2012) Genetics; Analysis of Genes and Genomes, 8th edition, Burlington: Jones and Barlett.</ref>.&nbsp; The base pairs are bound by [[Hydrogen bonds|hydrogen bonds]], although the number of H-bonds differs between base pairs. G-C base pairs are bound by three (3) hydrogen bonds whilst, A-T base pairs are bound by two (2) hydrogen bonds as illustrated in the figure on the right <ref>Becker., Kleinsmith., Hardin and Bertoni (2009) The World of the Cell, Seventh Edition, San Francisco: Pearson Education.</ref>.  
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Adenine (A) binds to thymine (T) whilst, guanine (G) binds to cytosine (C). However, in RNA&nbsp;unracil (U)&nbsp;is substituted for thymine (T). This base pairing is referred to as complementary base pairing, hence the base pairs are called complementary [[Base pairs|base pairs]]&nbsp;<ref>Hartl D., Ruvolo M. (2012) Genetics; Analysis of Genes and Genomes, 8th edition, Burlington: Jones and Barlett.</ref>.&nbsp; The base pairs are bound together by [[Hydrogen bonds|hydrogen bonds]], although the number of H-bonds differs between base pairs. G-C base pairs are bound by three (3) hydrogen bonds whilst, A-T base pairs are bound by two (2) hydrogen bonds as illustrated in the figure on the right <ref>Becker., Kleinsmith., Hardin and Bertoni (2009) The World of the Cell, Seventh Edition, San Francisco: Pearson Education.</ref>.  
  
<span class="Apple-style-span" style="font-size: 18px; font-weight: bold; ">Importance &nbsp; &nbsp;</span>
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Importance &nbsp; &nbsp;  
  
Watson-Crick base&nbsp;pairing is of very great importance as it&nbsp;is a deciding factor in [[Semi-conservative replication|DNA&nbsp;Replication]]&nbsp;<ref name="null">Genetic Science Learning Center (2011) Build a DNA Molecule. Learn.Genetics. Available at: http://learn.genetics.utah.edu/content/begin/dna/builddna/. [Last assessed: 26/11/2011] University of Utah</ref>. It ensures that pairs form between complementary bases only. The formation of base pairs between two non-complementary bases&nbsp;results in&nbsp;[[Mutations|gene mutations]] which can be detrimental to development of an organism.<span class="Apple-style-span" style="font-size: 13px; font-weight: normal; ">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;</span>
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Watson-Crick base&nbsp;pairing is of very great importance as it&nbsp;is a deciding factor in [[Semi-conservative replication|DNA&nbsp;Replication]]&nbsp;<ref name="null">Genetic Science Learning Center (2011) Build a DNA Molecule. Learn.Genetics. Available at: http://learn.genetics.utah.edu/content/begin/dna/builddna/. [Last assessed: 26/11/2011] University of Utah</ref>. It ensures that pairs form between complementary bases only. The formation of base pairs between two non-complementary bases&nbsp;results in&nbsp;[[Mutations|gene mutations]] which can be detrimental to development of an organism.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;  
  
 
=== Background  ===
 
=== Background  ===
  
In 1953, [[James_watson|James D Watson]] and [[Francis_Crick|Francis Crick]] discovered the structure of DNA using X ray Crystallography. They worked out that [[DNA|DNA]] was a double helix using Rosalind Franklin's X ray diffraction pattern&nbsp;<ref>BBC NEWS. Science/Nature Available: http://news.bbc.co.uk/1/hi/sci/tech/2804545.stmfckLR[accessed 2 December 2011]</ref>.&nbsp;At first, it was thought that [[DNA|DNA]] was made up of many chemicals, which proved too difficult to analyse, but the researchers persisitence led to the discovery of complementary base pairing<span class="Apple-style-span" style="font-size: 13px; font-weight: normal; ">&nbsp;<ref>DNA tutorial Available :http://www.dnatutorial.com/BasePairing.shtml [accessed 2 December 2011]</ref>.</span>
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In 1953, [[James watson|James D Watson]] and [[Francis Crick|Francis Crick]] discovered the structure of DNA using [[X ray Crystallography|X ray Crystallography]]. They worked out that [[DNA|DNA]] was a double helix using [[Rosalind_Franklin|Rosalind Franklin's]] X ray diffraction pattern&nbsp;<ref>BBC NEWS. Science/Nature Available: http://news.bbc.co.uk/1/hi/sci/tech/2804545.stmfckLR[accessed 2 December 2011]</ref>.&nbsp;At first, it was thought that [[DNA|DNA]] was made up of many chemicals, which proved too difficult to analyse, but the researchers persisitence led to the discovery of complementary base pairing&nbsp;<ref>DNA tutorial Available :http://www.dnatutorial.com/BasePairing.shtml [accessed 2 December 2011]</ref>.  
  
 
=== References  ===
 
=== References  ===
  
 
<references />
 
<references />

Latest revision as of 20:53, 24 October 2012

James Watson and Francis Crick
Figure 1.1 A-T and G-C base pairs

DNA consists of two types of bases, namely; purines and pyrimidines. There are two types of purines: adenine and guanine, as well as two types of Pyrimidines: cytosine and thymine. In the Watson-Crick DNA base pairing model a purine always binds with a pyrimidine, however, each purine binds to one particular type of pyrimidine.

Adenine (A) binds to thymine (T) whilst, guanine (G) binds to cytosine (C). However, in RNA unracil (U) is substituted for thymine (T). This base pairing is referred to as complementary base pairing, hence the base pairs are called complementary base pairs [1].  The base pairs are bound together by hydrogen bonds, although the number of H-bonds differs between base pairs. G-C base pairs are bound by three (3) hydrogen bonds whilst, A-T base pairs are bound by two (2) hydrogen bonds as illustrated in the figure on the right [2].

Importance    

Watson-Crick base pairing is of very great importance as it is a deciding factor in DNA Replication [3]. It ensures that pairs form between complementary bases only. The formation of base pairs between two non-complementary bases results in gene mutations which can be detrimental to development of an organism.                      

Background

In 1953, James D Watson and Francis Crick discovered the structure of DNA using X ray Crystallography. They worked out that DNA was a double helix using Rosalind Franklin's X ray diffraction pattern [4]. At first, it was thought that DNA was made up of many chemicals, which proved too difficult to analyse, but the researchers persisitence led to the discovery of complementary base pairing [5].

References

  1. Hartl D., Ruvolo M. (2012) Genetics; Analysis of Genes and Genomes, 8th edition, Burlington: Jones and Barlett.
  2. Becker., Kleinsmith., Hardin and Bertoni (2009) The World of the Cell, Seventh Edition, San Francisco: Pearson Education.
  3. Genetic Science Learning Center (2011) Build a DNA Molecule. Learn.Genetics. Available at: http://learn.genetics.utah.edu/content/begin/dna/builddna/. [Last assessed: 26/11/2011] University of Utah
  4. BBC NEWS. Science/Nature Available: http://news.bbc.co.uk/1/hi/sci/tech/2804545.stmfckLR[accessed 2 December 2011]
  5. DNA tutorial Available :http://www.dnatutorial.com/BasePairing.shtml [accessed 2 December 2011]
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