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RNA stands for ribonucleic acid. It is made up of a series of [[Nucleotides|nucleotides]] joined by 3'-5' | RNA stands for ribonucleic acid. It is made up of a series of [[Nucleotides|nucleotides]] joined by 3'-5'[[Phosphodiester|phosphodiester]] bonds. RNAforms 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]]. The phosphodiester bonds that make up the backbone have a negative charge, this ensures it cannot be hydrolysed by nucleophilic attack, for example by hydroxide ions, as the negative charges repel each other.<ref>Berg, J.M., Tymoczko, J.L., and Stryer, L. (2011). Biochemistry. 7th ed. New York: W. H. Freeman and Company. 115.</ref> | ||
Attached to the backbone are 4 [[Base|bases]], in a similar way to DNA, in which | 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 RNAC 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 == | ||
1. [[MRNA|mRNA]] – messenger RNA <ref>Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 119</ref> | 1. [[MRNA|mRNA]] – messenger RNA <ref>Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 119</ref> | ||
**Single polynucleotide strand madein the nucleus during [[Transcription|transcription]] | |||
**DNA is transcribed into mRNA, therefore the mRNA and the DNA are complementary | |||
**mRNA carries the [[Genetic code|genetic code]] from the DNA in the nucleus to the [[Ribosomes|ribosomes]] in the [[Cytoplasm|cytoplasm]]<br>** This mRNAis then used as a template for [[Translation|translation]] into a functional protein<br>** mRNAis also used to make copy DNA([[CDNA|cDNA]]) | |||
2. [[TRNA|tRNA]] – transfer RNA<ref>Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 120</ref> | |||
<br> | **Single polynucleotide strand whichis folded into a clover shape, held together by [[Hydrogen bonds|hydrogen bonds]]<br>** Consists of a specificsequence of three unpairedbases boundto a complementary [[Codon|codon]]([[Anticodon|anticodon]])and an[[Amino acid|amino acid]] bindingsite | ||
**Found in the [[Cytoplasm|cytoplasm]], where it is involved in translation | |||
**This [[Molecule|moleculecarriesamino]] acids tothe ribosomes where a [[Polypeptide|polypeptide]] is formed, the sequence of which was determined by the [[MRNA|mRNA]]. | |||
3. [[RRNA|rRNA]] – ribosomal RNA<ref>Berg JM, Tymoczko JL and Stryer L, 2007, Biochemistry 6th edition, NY, W. H Freeman and Company, page 120</ref> | |||
**This is the RNAwhich forms[[Ribosomes|ribosomes]] | |||
**It acts as a catalyst for [[Proteins|protein]] synthesis | |||
**It is synthesised in the [[Nucleolus|nucleolus]] | |||
- 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 | 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> | ||
**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<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> | |||
**used to process and modify rRNA chemically | |||
6. scaRNA - small cajal 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> | |||
**a class of snoRNAs | |||
**locate at the Cajal body | |||
**to modify snoRNA and snRNA | |||
7. miRNA - microRNA<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> | |||
**non-coding RNA molecule | |||
**containing approximately 22 nucleotides | |||
**regulate gene expression by blocking translation of selective mRNA | |||
8. siRNA - small interfering 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> | |||
**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<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| | 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|riboswitchesin]] 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 15:24, 1 December 2015
RNA stands for ribonucleic acid. It is made up of a series of nucleotides joined by 3'-5'phosphodiester bonds. RNAforms a polynucleotide strand with a sugar-phosphate backbone. Unlike DNA, RNA has a ribose sugar, which means that it has a 2` hydroxyl group. The phosphodiester bonds that make up the backbone have a negative charge, this ensures it cannot be hydrolysed by nucleophilic attack, for example by hydroxide ions, as the negative charges repel each other.[1]
Attached to the backbone are 4 bases, in a similar way to DNA, in whichcytosine (C) pairs with guanine (G) and thymine (T) pairs with adenine (A). However in RNAC pairs with G, but A pairs with uracil (U) instead of T[2]. RNA is typically single-stranded, although regions can form where the RNA loops back on itself, to produce "hairpin"secondary structures.[3]
RNA involved in gene expression
- Single polynucleotide strand madein 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 mRNAis then used as a template for translation into a functional protein
** mRNAis also used to make copy DNA(cDNA)
- Single polynucleotide strand whichis folded into a clover shape, held together by hydrogen bonds
** Consists of a specificsequence of three unpairedbases boundto a complementary codon(anticodon)and anamino acid bindingsite - Found in the cytoplasm, where it is involved in translation
- This moleculecarriesamino acids tothe ribosomes where a polypeptide is formed, the sequence of which was determined by the mRNA.
- Single polynucleotide strand whichis folded into a clover shape, held together by hydrogen bonds
- 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[7]
- 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[8]
- used to process and modify rRNA chemically
6. scaRNA - small cajal RNA[9]
- a class of snoRNAs
- locate at the Cajal body
- to modify snoRNA and snRNA
7. miRNA - microRNA[10]
- non-coding RNA molecule
- containing approximately 22 nucleotides
- regulate gene expression by blocking translation of selective mRNA
8. siRNA - small interfering RNA[11]
- 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[12]. Beasides, non-coding RNAs also have many applications but many revolve around regulation of gene expression, such as riboswitchesin bacteria and miRNAs involved in RNAi(RNA interference) in animals[13].
References
- ↑ Berg, J.M., Tymoczko, J.L., and Stryer, L. (2011). Biochemistry. 7th ed. New York: W. H. Freeman and Company. 115.
- ↑ 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