Nucleic acids

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A nucleic acid (such as DNA or RNA) are linear molecules found in the form of a polymer, and carry information which is able to be passed on from generation to generation. They are made up of nucleotides that are linked together, which is composed of a sugar, a phosphate and a base. This forms the backbone to the structure, whilst the bases carry the genetic information [1].

Nucleic acids allow the transfer of genetic information from generation to generation by means of DNA replication.

There are two types of nucleic acid:

  1. DNA
  2. RNA (appears in several forms)

Nucleic acids have 3 main features:

  1. Nitrogenous base.
  2. 5 Carbon sugar (pentose).
  3. Phosphate group.

The Nitrogenous group has 4 variants in DNA, these are:

  1. Adenine (A)
  2. Thymine (T)
  3. Guanine (G)
  4. Cytosine (C)

RNA substitutes Uracil for Thymine.

Adenine is complementary to Thymine and Guanine is complementary the Cytosine. Hydrogen bonds form between complementary bases of different nucleic acids. 2 hydrogen bonds form between A and T and 3 between G and C.

Covalent phosphodiester bonds form between the phosphate groups of neighbouring nucleic acids [2].

Contents

RNA and DNA

RNA and DNA are nucleic acids involved in transcription and translation. DNA is transcribed into a form of RNA called messenger RNA (MRNA), which is then translated into a Protein. Both of these nucleic acids differ slightly in terms of the sugar component and one of the bases in their structure [3].

DNA

Sugar - The sugar which is part of the structure of DNA is deoxyribose, hence the name, deoxyribonucelic acid. The second carbon atom in the sugar does not have an oxygen atom which would usually be found on the second carbon of the sugar ribose [4].

Bases - The four bases found in DNA are Adenineguanine (derivatives of purine), cytosine and thymine (derivatives of pyrimidine).[5]

RNA

Sugar - Unlike DNA, the sugar which forms the part of the backbone for RNA is ribose. This contains a hydroxyl group on the second carbon atom, which is not present on deoxyribose [6]. This 2' hydroxyl group makes RNA a more unstable molecule than DNA. 

Bases - Similarly to DNA, the four bases of RNA are adenine, guanine, cytosine, and a different base, uracil, which is a pyrimidine derivative [7].

References

  1. Berg J.M, Tymoczko J.L, Stryer L (2007) Biochemistry Sixth Edition: 107
  2. http://biology.about.com/od/molecularbiology/a/nucleicacids.htm
  3. Berg J.M, Tymoczko J.L, Stryer L (2007) Biochemistry Sixth Edition: 107-108
  4. Berg J.M, Tymoczko J.L, Stryer L (2007) Biochemistry Sixth Edition: 108
  5. Berg J.M, Tymoczko J.L, Stryer L (2007) Biochemistry Sixth Edition: 109
  6. Berg J.M, Tymoczko J.L, Stryer L (2007) Biochemistry Sixth Edition: 109
  7. Berg J.M, Tymoczko J.L, Stryer L (2007) Biochemistry Sixth Edition: 109

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