RNA: Difference between revisions
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RNA stands for ribonucleic acid. It is made up of a series of nucleotides joined by 3' | 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 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 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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- DNA is transcribed into mRNA, therefore the mRNA and the DNA are complementary | - 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 | - mRNA carries the [[Genetic code|genetic code]] from the DNA in the nucleus to the ribosomes in the cytoplasm<br> - This mRNA is then used as a template for [[Translation|translation]] into a functional protein<br> - mRNA is also used to make copy DNA ([[CDNA|cDNA]]) | ||
<br>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>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> | ||
- Single polynucleotide strand which is folded into a clover shape, held together by [[Hydrogen bonds|hydrogen bonds]]<br> - Consists of a specific sequence of three unpaired bases bound to a complementary codon ([[Anticodon|anticodon]]) and an amino acid binding site | - Single polynucleotide strand which is folded into a clover shape, held together by [[Hydrogen bonds|hydrogen bonds]]<br> - Consists of a specific sequence of three unpaired bases bound to a complementary codon ([[Anticodon|anticodon]]) and an amino acid binding site | ||
- Found in the cytoplasm, where it is involved in | - Found in the cytoplasm, where it is involved in translation | ||
- This [[Molecule|molecule]] carries amino acids to the ribosomes where a [[Polypeptide|polypeptide]] is formed, the sequence of which was determined by the [[MRNA|mRNA]]. | - This [[Molecule|molecule]] carries amino acids to the ribosomes where a [[Polypeptide|polypeptide]] is formed, the sequence of which was determined by the [[MRNA|mRNA]]. | ||
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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. | 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. | ||
RNA can also exist in non coding forms. These non coding RNAs have many applications but many revolve around regulation of gene expression, such as [[Riboswitches| | RNA can also exist in non coding forms. These non coding RNAs have many applications but many revolve around regulation of 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 19:30, 22 December 2011
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.
RNA can also exist in non coding forms. These non coding RNAs 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 [6].
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, pg 493