Watson-Crick base pairing

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= 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]]
  
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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.
  
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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.
  
=== Background ===
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=== Importance&nbsp;&nbsp;&nbsp;&nbsp;  ===
  
In 1953, James D Watson and 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.<ref>BBC NEWS. Science/Nature Available: http://news.bbc.co.uk/1/hi/sci/tech/2804545.stm
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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.  
[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.
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=== References  ===
  
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<references />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
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=== Background  ===
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In 1953, James D Watson and 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.
  
 
=== Pairing  ===
 
=== Pairing  ===
  
It has been found that DNA contains four bases namly adenine (A), thymine(T), guanine(G) and cytosine(C). A and T occur in same amounts and C and G occur in same amounts, thus the two possible base pair combinations.<ref>DNA tutorial Available :http://www.dnatutorial.com/BasePairing.shtml [accessed 2 December 2011]</ref>
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It has been found that DNA contains four bases namly adenine (A), thymine(T), guanine(G) and cytosine(C). A and T occur in same amounts and C and G occur in same amounts, thus the two possible base pair combinations&nbsp;<ref>DNA tutorial Available :http://www.dnatutorial.com/BasePairing.shtml [accessed 2 December 2011]</ref>.
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=== References ===
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<references />

Revision as of 10:01, 3 December 2011

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); although in RNA unracil (U) is substituted for thymine (T). This base pairing is referred to as complementary, hence the base pairs are called complementary base pairs [1].  The base pairs are bound 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.

Contents

Importance    

Watson-Crick base pairing is of very great importance as it is a deciding factor in DNA Replication [2]. 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.

References

  1. Hartl D., Ruvolo M. (2012) Genetics; Analysis of Genes and Genomes, 8th edition, Burlington: Jones and Barlett.
  2. 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
                             

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 [1]. 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.

Pairing

It has been found that DNA contains four bases namly adenine (A), thymine(T), guanine(G) and cytosine(C). A and T occur in same amounts and C and G occur in same amounts, thus the two possible base pair combinations [2].

References

  1. BBC NEWS. Science/Nature Available: http://news.bbc.co.uk/1/hi/sci/tech/2804545.stmfckLR[accessed 2 December 2011]
  2. DNA tutorial Available :http://www.dnatutorial.com/BasePairing.shtml [accessed 2 December 2011]
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