DNA bases: Difference between revisions
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[[DNA|DNA]] | The [[DNA|DNA double helix]] consists of two strands of [[Complementary strand|complementary]] [[Polynucleotide Chain|polynucleotide]] chains which are made up of four [[Nucleotide|nucleotides]]. The four nucleotide bases are: | ||
*[[Adenine|Adenine]] (A) | *[[Adenine|Adenine]] (A) | ||
*[[Cytosine|Cytosine]] (C) | *[[Cytosine|Cytosine]] (C) | ||
*[[Thymine|Thymine]] | *[[Thymine|Thymine]] (T) | ||
*[[Guanine|Guanine]] (G) | *[[Guanine|Guanine]] (G)<ref>Daniel.L.Hartl and Maryellen Ruvolo (2012) Eighth Edition, Genetics: analysis of genes and genomes,Jones and Bartlett Learning International Student Edition, Editor: Megan.R.Turner, USA Chapter 1 page 7</ref>. | ||
Each base has the same basic structure, a [[Deoxyribose|deoxyribose]] five carbon sugar with a base attached to C<sub>1 </sub>and a [[Phosphate group|phosphate]] group attached to C<sub>5</sub>. This structure gives the nucleotide, and subsequently the DNA strand [[DNA Structure|polarity]]<ref>Alberts et. al. (2008) Molecular Biology of the Cell, 5th Edition, United States, Garland Publishing Inc, pp 116</ref>. The end with the phosphate group is denoted as the 5' end. And the end with the free hydroxyl group on C<sub>3</sub> is denoted as the 3' end. | |||
= References = | The nucleotide bases are joined by a [[Phosphodiester bond|phosphodiester linkage]]<ref>Alberts et. al. (2008) Molecular Biology of the Cell, 5th Edition, United States, Garland Publishing Inc, pp 197-199</ref>. This is a covalent bond that forms between C<sub>5 </sub>on one nucleotide and C<sub>3 </sub>of the neighbouring nucleotide<ref>Alberts et. al. (2008) Molecular Biology of the Cell, 5th Edition, United States, Garland Publishing Inc, pp 117</ref>. This forms the [[Sugar phosphate backbone|sugar phosphate backbone]] of DNA. | ||
[[Watson-Crick base pairing|Watson-Crick base pairing]] occurs between [[Adenine|Adenine]] and [[Thymine|Thymine]], Cytosine and Guanine. The base pairs form [[Hydrogen bonds|hydrogen bonds]]. [[Adenine|Adenine]] (A) and [[Guanine|Guanine]] (G) are [[Purines|purines]] as they both have double-ring structure. Whereas, [[Thymine|thymine]] (T) and [[Cytosine|cytosine]] (C) are called [[Pyrimidines|pyrimidines]] as they both have a single-ring structure. Due to the different structure of the bases, A and T form two hydrogen bonds whereas C and G form three hydrogen bonds. It is by complementary base pairing that the two strands of DNA are held together<ref>Daniel.L.Hartl and Maryellen Ruvolo (2012) Eighth Edition, Genetics: analysis of genes and genomes, Jones and Bartlett Learning International Student Edition, Editor: Megan.R.Turner, USA Chapter 2 pager 42-47</ref>. | |||
=== References === | |||
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Latest revision as of 11:26, 22 October 2018
The DNA double helix consists of two strands of complementary polynucleotide chains which are made up of four nucleotides. The four nucleotide bases are:
Each base has the same basic structure, a deoxyribose five carbon sugar with a base attached to C1 and a phosphate group attached to C5. This structure gives the nucleotide, and subsequently the DNA strand polarity[2]. The end with the phosphate group is denoted as the 5' end. And the end with the free hydroxyl group on C3 is denoted as the 3' end.
The nucleotide bases are joined by a phosphodiester linkage[3]. This is a covalent bond that forms between C5 on one nucleotide and C3 of the neighbouring nucleotide[4]. This forms the sugar phosphate backbone of DNA.
Watson-Crick base pairing occurs between Adenine and Thymine, Cytosine and Guanine. The base pairs form hydrogen bonds. Adenine (A) and Guanine (G) are purines as they both have double-ring structure. Whereas, thymine (T) and cytosine (C) are called pyrimidines as they both have a single-ring structure. Due to the different structure of the bases, A and T form two hydrogen bonds whereas C and G form three hydrogen bonds. It is by complementary base pairing that the two strands of DNA are held together[5].
References
- ↑ Daniel.L.Hartl and Maryellen Ruvolo (2012) Eighth Edition, Genetics: analysis of genes and genomes,Jones and Bartlett Learning International Student Edition, Editor: Megan.R.Turner, USA Chapter 1 page 7
- ↑ Alberts et. al. (2008) Molecular Biology of the Cell, 5th Edition, United States, Garland Publishing Inc, pp 116
- ↑ Alberts et. al. (2008) Molecular Biology of the Cell, 5th Edition, United States, Garland Publishing Inc, pp 197-199
- ↑ Alberts et. al. (2008) Molecular Biology of the Cell, 5th Edition, United States, Garland Publishing Inc, pp 117
- ↑ Daniel.L.Hartl and Maryellen Ruvolo (2012) Eighth Edition, Genetics: analysis of genes and genomes, Jones and Bartlett Learning International Student Edition, Editor: Megan.R.Turner, USA Chapter 2 pager 42-47