RNA: Difference between revisions
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RNA stands for ribonucleic acid. It is made up of a series of [[Nucleotides|nucleotides]] joined by 3'-5' [[Phosphodiester|phosphodiester]] bonds. RNA forms a polynucleotide strand with a sugar-phosphate backbone. Unlike [[DNA]], RNA has a [[Ribose|ribose]] sugar, which means that it has a 2` [[Hydroxyl group|hydroxyl group]]. | RNA stands for ribonucleic acid. It is made up of a series of [[Nucleotides|nucleotides]] joined by 3'-5' [[Phosphodiester|phosphodiester]] bonds. RNA forms a polynucleotide strand with a sugar-phosphate backbone. Unlike [[DNA]], RNA has a [[Ribose|ribose]] sugar, which means that it has a 2` [[Hydroxyl group|hydroxyl group]]. | ||
Attached to the backbone are 4 [[Base|bases]], in a similar way to DNA, in which [[Cytosine|cytosine]] (C) pairs with [[Guanine|guanine]] (G) and [[Thymine|thymine]] (T) pairs with [[Adenine|adenine]] (A). However in RNA C pairs with G, but A pairs with [[ | Attached to the backbone are 4 [[Base|bases]], in a similar way to DNA, in which [[Cytosine|cytosine]] (C) pairs with [[Guanine|guanine]] (G) and [[Thymine|thymine]] (T) pairs with [[Adenine|adenine]] (A). However in RNA C pairs with G, but A pairs with [[Uracil|uracil]] (U) instead of T <ref>Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 109</ref>. RNA is typically single-stranded, although regions can form where the RNA loops back on itself, to produce "[[Hairpin|hairpin]]" secondary structures.<ref name="null">Lyons, I, 2011. Biomedical Science Lecture Notes. 1st ed. Oxford: Wiley-Blackwell, p21-23</ref> | ||
== RNA involved in gene expression == | == RNA involved in gene expression == | ||
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- It is synthesised in the [[Nucleolus|nucleolus]] | - It is synthesised in the [[Nucleolus|nucleolus]] | ||
- rRNA molecules do not code for protein | - rRNA molecules do not code for protein<br> | ||
The three RNAs all work together to convert the initial DNA molecule into a protein. All three of these types of RNA are synthesised by RNA Polymerase.<br> | |||
The three RNAs all work together to convert the initial DNA molecule into a protein. All three of these types of RNA are synthesised by RNA Polymerase. | |||
<br> | |||
4. snRNA -- small nuclear RNA<ref>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</ref> | 4. snRNA -- small nuclear RNA<ref>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</ref> | ||
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- double stranded RNA molecules | - double stranded RNA molecules | ||
- turn off gene expression by directing degradation of selective mRNA and the establishment of compact chromatin structures | - turn off gene expression by directing degradation of selective mRNA and the establishment of compact chromatin structures<br> | ||
<br> | |||
RNA can also exist in non coding forms. These non-coding RNAs function in diverse cell processes, such as telomere synthesis, transport of proteins intot the endoplasmic recticulum and X-chromosome inactivation<ref>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</ref>. Beasides, non-coding RNAs also have many applications but many revolve around regulation of [[Gene|gene]] expression, such as [[Riboswitches|riboswitches]] in bacteria and miRNAs involved in [[RNAi]] (RNA interference) in animals <ref>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</ref>. | RNA can also exist in non coding forms. These non-coding RNAs function in diverse cell processes, such as telomere synthesis, transport of proteins intot the endoplasmic recticulum and X-chromosome inactivation<ref>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</ref>. Beasides, non-coding RNAs also have many applications but many revolve around regulation of [[Gene|gene]] expression, such as [[Riboswitches|riboswitches]] in bacteria and miRNAs involved in [[RNAi]] (RNA interference) in animals <ref>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</ref>. | ||
== References == | == References == | ||
<references /> | <references /> | ||
Revision as of 23:46, 27 November 2014
RNA stands for ribonucleic acid. It is made up of a series of nucleotides joined by 3'-5' phosphodiester bonds. RNA forms a polynucleotide strand with a sugar-phosphate backbone. Unlike DNA, RNA has a ribose sugar, which means that it has a 2` hydroxyl group.
Attached to the backbone are 4 bases, in a similar way to DNA, in which cytosine (C) pairs with guanine (G) and thymine (T) pairs with adenine (A). However in RNA C pairs with G, but A pairs with uracil (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]
RNA involved in gene expression
1. mRNA – messenger RNA [3]
- Single polynucleotide strand made in the nucleus during transcription
- DNA is transcribed into mRNA, therefore the mRNA and the DNA are complementary
- mRNA carries the genetic code from the DNA in the nucleus to the ribosomes in the cytoplasm
- This mRNA is then used as a template for translation into a functional protein
- mRNA is also used to make copy DNA (cDNA)
- Single polynucleotide strand which is folded into a clover shape, held together by hydrogen bonds
- Consists of a specific sequence of three unpaired bases bound to a complementary codon (anticodon) and an amino acid binding site
- Found in the cytoplasm, where it is involved in translation
- This molecule carries amino acids to the ribosomes where a polypeptide is formed, the sequence of which was determined by the mRNA.
3. rRNA – ribosomal RNA [5]
- This is the RNA which forms ribosomes
- It acts as a catalyst for protein synthesis
- It is synthesised in the nucleolus
- rRNA molecules do not code for protein
The three RNAs all work together to convert the initial DNA molecule into a protein. All three of these types of RNA are synthesised by RNA Polymerase.
4. snRNA -- small nuclear RNA[6]
- commonly known as U-RNA
- function in various nuclear processes
- function in the splicing of pre-mRNA
- transcribed by either RNA polymerase II or RNA polymerase III
5. snoRNA -- small nucleolar RNA[7]
- used to process and modify rRNA chemically
6. scaRNA -- small cajal RNA[8]
- a class of snoRNAs
- locate at the Cajal body
- to modify snoRNA and snRNA
7. miRNA -- microRNA[9]
- non-coding RNA molecule
- containing approximately 22 nucleotides
- regulate gene expression by blocking translation of selective mRNA
8. siRNA -- small interfering RNA[10]
- also known as silencing RNA
- double stranded RNA molecules
- turn off gene expression by directing degradation of selective mRNA and the establishment of compact chromatin structures
RNA can also exist in non coding forms. These non-coding RNAs function in diverse cell processes, such as telomere synthesis, transport of proteins intot the endoplasmic recticulum and X-chromosome inactivation[11]. Beasides, 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 [12].
References
- ↑ Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 109
- ↑ Lyons, I, 2011. Biomedical Science Lecture Notes. 1st ed. Oxford: Wiley-Blackwell, p21-23
- ↑ Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 119
- ↑ Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 120
- ↑ Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 120
- ↑ 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
- ↑ 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
- ↑ 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
- ↑ 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
- ↑ 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
- ↑ 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
- ↑ 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