RNA

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RNA or ribonucleic acid, is made up of a series of nucleotides joined by 3'-5' phosphodiester bonds. RNA forms a polynucleotide strand with a sugar-phosphate backbone. The phosphodiester bonds that makes up the backbone has a negative charge, which protects the molecule from being hydrolyzed by a nucleophilic attack as the negative charges of the backbone and nucleophile repel each other.

RNA differs from DNA as it has a ribose sugar, whereas DNA has a deoxyribose sugar. The ribose sugar contains a 2` hydroxyl group and DNA contains a 3' hydroxyl group. Like DNA, RNA has four nucleotide bases: cytosine (C), guanine (G), adenine (A) and uracil (DNA has a thymine base rather than uracil) that are attached to the backbone. In RNA, C pairs with G, but A pairs with U instead of T[1]. RNA is typically single-stranded, although regions can form where the RNA loops back on itself, to produce "hairpin" secondary structures[2], an example of this is in the termination step of transcription.

Contents

RNA involved in gene expression

1. mRNA – messenger RNA[3]

2. tRNA – transfer RNA[5]

3. rRNA – ribosomal RNA[6]

The three RNAs all work together to convert the initial DNA molecule into a protein. All three of these types of RNA are synthesized by RNA Polymerase.

4. snRNA - small nuclear RNA[7]

5. snoRNA - small nucleolar RNA[8]

6. scaRNA - small cajal RNA[9]

7. miRNA - microRNA[10]

8. siRNA - small interfering RNA[11]

RNA can also exist in non-coding forms. These non-coding RNAs function in diverse cell processes, such as telomere synthesis, transport of proteins into the endoplasmic reticulum and X-chromosome inactivation[12]. Besides, non-coding RNAs also have many applications but many revolve around regulation of gene expression, such as riboswitches in bacteria and miRNAs involved in RNAi (RNA interference) in animals[13].

References

  1. Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 109
  2. Lyons, I, 2011. Biomedical Science Lecture Notes. 1st ed. Oxford: Wiley-Blackwell, p21-23
  3. Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 119
  4. https://en.wikipedia.org/wiki/Messenger_RNA
  5. Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 120
  6. Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 120
  7. Alberts, B., Johnson, A., Lewis, J., Raff, M.,Roberts, K., Walter, P. (2008). Molecular Biology of The Cell 5th edition. New York: Garland Science. Page 336
  8. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P. (2008). Molecular Biology of The Cell 5th edition. New York: Garland Science. Page 336
  9. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P. (2008). Molecular Biology of The Cell 5th edition. New York: Garland Science. Page 336
  10. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P. (2008). Molecular Biology of The Cell 5th edition. New York: Garland Science. Page 336
  11. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P. (2008). Molecular Biology of The Cell 5th edition. New York: Garland Science. Page 336
  12. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P. (2008). Molecular Biology of The Cell 5th edition. New York: Garland Science. Page 336
  13. Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P,2008, Molecular Biology of the Cell,5th Edition, New York, Garland Science, pg 493
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