The School of Biomedical Sciences Wiki - User contributions [en]

Gene transcription

2018-12-05T18:43:11Z

180143483: image added

When a gene is copied from its [[DNA|DNA]] form to its [[RNA|RNA]] form<ref>https://en.wikipedia.org/wiki/Transcription_(biology)</ref>. The [[Antisense strand|antisense strand]] of DNA acts as a template strand and is used by [[RNA polymerase|RNA polymerases]] to synthesise mRNA . In eukaryotes, the mRNA produced in transcription is modified through the addition of a  polyA tail and 5' cap. The modified [[MRNA|mRNA]] can then be used in [[Translation|translation]] at the [[Ribosome|ribosomes]] by [[TRNA|tRNA]] to synthesise a [[Polypeptide|polypeptide]], allowing the gene to be expressed<ref>Khan Academy. Overview of transcription: in transcription, the DNA sequence of a gene is transcribed (copied out) to make an RNA molecule. Date published unknown [Accessed 5/12/18]; Available from: https://www.khanacademy.org/science/biology/gene-expression-central-dogma/transcription-of-dna-into-rna/a/overview-of-transcription</ref>. 

The process of transcription involves three major stages: initiation, elongation and termination. During initiation, RNA polymerase enzyme binds to the [[Promoter|promotor sequence]] upstream of the gene on the antisense strand, this is the closed complex. Binding of the RNA polymerase to the promoter causes local denaturation of the DNA so it starts to unwind, this is known as the open complex. The next stage of transcription is elongation where the strand of mRNA is synthesised. RNA polymerase synthesises mRNA using RNA [[Nucleotides|nucleotides]] and the principles of [[Complementary base pairing|complementary base pairing]], meaning that the mRNA synthesised is identical to the sense strand but with [[Uracil|uracil]] instead of [[Thymine|thymine]]. Transcription stops when the RNA polymerase [[Enzyme|enzyme reaches]] a [[Terminator sequence|terminator]] sequence, the mRNA then detaches from the DNA<ref>Bozeman Science. Steps of Genetic Transcription. Date published unknown [Accessed 5/12/18]; Available from: https://courses.lumenlearning.com/wm-biology1/chapter/reading-steps-of-genetic-transcription/</ref>. 

 

[[Image:Transcription for WIKI.png|Three stages of transcription: Initiation, elongation and termination]] 

 

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File:Transcription for WIKI.png

2018-12-05T18:31:07Z

180143483: Diagram showing the three stages of gene transcription

Diagram showing the three stages of gene transcription

Gene transcription

2018-12-05T18:29:16Z

180143483: Added information on the process of gene transcription and references

When a gene is copied from its [[DNA|DNA]] form to its [[RNA|RNA]] form<ref>https://en.wikipedia.org/wiki/Transcription_(biology)</ref>. The [[Antisense_strand|antisense strand]] of DNA acts as a template strand and is used by [[RNA_polymerase|RNA polymerases]] to synthesise mRNA . In eukaryotes, the mRNA produced in transcription is modified through the addition of a  polyA tail and 5' cap. The modified [[MRNA|mRNA]] can then be used in [[Translation|translation]] at the [[Ribosome|ribosomes]] by [[TRNA|tRNA]] to synthesise a [[Polypeptide|polypeptide]], allowing the gene to be expressed<ref>Khan Academy. Overview of transcription: in transcription, the DNA sequence of a gene is transcribed (copied out) to make an RNA molecule. Date published unknown [Accessed 5/12/18]; Available from: https://www.khanacademy.org/science/biology/gene-expression-central-dogma/transcription-of-dna-into-rna/a/overview-of-transcription</ref>. 

Transcription includes three major stages: initiation, elongation and termination. During initiation the RNA polymerase enzyme binds to the [[Promoter|promotor ]]sequence upstream of the gene on the antisense strand, this is the closed complex. Binding of the RNA polymerase to the promoter causes local denaturation of the DNA so it starts to unwind, this is known as the open complex. The next stage of transcription is elongation where the strand of mRNA is synthesised. RNA polymerase synthesises mRNA using [[Complementary_base_pairing|complementary base pairing ]]and RNA [[Nucleotides|nucleotides]], meaning that the mRNA is identical to the sense strand but with [[Uracil|uracil]] instead of [[Thymine|thymine]]. Transcription stops when RNA polymerase reaches a [[Terminator_sequence|terminator]] sequence, the mRNA then detaches from the DNA<ref>Bozeman Science. Steps of Genetic Transcription. Date published unknown [Accessed 5/12/18]; Available from: https://courses.lumenlearning.com/wm-biology1/chapter/reading-steps-of-genetic-transcription/</ref>. 

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Ubiquinone

2018-12-05T12:59:49Z

180143483: Reference changed

Ubiquinone is a [[Quinone|quinone]] found in the [[Lipid bilayer|lipid bilayer]] and involved in the respiratory [[Electron transport chain|electron transport chain]] as an [[Electron carrier|electron carrier]] <ref>Alberts et al (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science. Chapter 14, Page 831</ref>. As an electron carrier ubiquinone donates or picks up [[Electrons|electrons]] in redox reactions. Ubiquinone is a small [[Hydrophobic|hydrophobic]] molecule ubiquinone has the ability to move easily through the [[Lipid bilayer|lipid bilayer]] and is not located in a fixed position. 

Ubiquinone, also known as [[Coenzyme Q|coenzyme Q]], plays an important role in the electron transport chain in mitochondria<ref>Sarah L Molyneux,1,* Joanna M Young,2 Christopher M Florkowski,1,2 Michael Lever,1 and Peter M George1. Coenzyme Q10: Is There a Clinical Role and a Case for Measurement? Clin Biochem Rev. 2008 May; 29(2): 71–82.</ref>. Coenzyme Q transfers electrons from complex I and complex II to complex III in the electron transport chain and is synthesised in all eukaryotic cells. Due to the fact that ubiquinone is essential in the production of [[ATP|ATP]], a deficiency in the [[Cofactor|cofactor]] can result in multiple diseases<ref>Trends Biochem Sci. 2017 Oct; 42(10): 824–843. Molecular Genetics of Ubiquinone Biosynthesis in Animals. Crit Rev Biochem Mol Biol. 2013 Jan-Feb; 48(1): 69–88.</ref>.

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Ubiquinone

2018-12-05T12:58:23Z

180143483:

Ubiquinone is a [[Quinone|quinone]] found in the [[Lipid bilayer|lipid bilayer]] and involved in the respiratory [[Electron transport chain|electron transport chain]] as an [[Electron carrier|electron carrier]] <ref>Alberts et al (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science. Chapter 14, Page 831</ref>. As an electron carrier ubiquinone donates or picks up [[Electrons|electrons]] in redox reactions. Ubiquinone is a small [[Hydrophobic|hydrophobic]] molecule ubiquinone has the ability to move easily through the [[Lipid bilayer|lipid bilayer]] and is not located in a fixed position. 

Ubiquinone, also known as [[Coenzyme Q|coenzyme Q]], plays an important role in the electron transport chain in mitochondria<ref>Sarah L Molyneux,1,* Joanna M Young,2 Christopher M Florkowski,1,2 Michael Lever,1 and Peter M George1. Coenzyme Q10: Is There a Clinical Role and a Case for Measurement? Clin Biochem Rev. 2008 May; 29(2): 71–82.</ref>. Coenzyme Q transfers electrons from complex I and complex II to complex III in the electron transport chain and is synthesised in all eukaryotic cells<ref>Trends Biochem Sci. 2017 Oct; 42(10): 824–843. Molecular Genetics of Ubiquinone Biosynthesis in Animals. Crit Rev Biochem Mol Biol. 2013 Jan-Feb; 48(1): 69–88.</ref> . Due to the fact that ubiquinone is essential in the production of [[ATP|ATP]], a deficiency in the [[Cofactor|cofactor]] can result in multiple diseases including [[Myopathies|myopathies <ref>Jonathan A. Stefely1,2,3 and David J. Pagliarini1,2,*. Biochemistry of Mitochondrial Coenzyme Q Biosynthesis. Trends Biochem Sci. 2017 Oct; 42(10): 824–843.</ref>]].

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Ubiquinone

2018-12-05T12:58:07Z

180143483: References and more information added

Ubiquinone is a [[Quinone|quinone]] found in the [[Lipid bilayer|lipid bilayer]] and involved in the respiratory [[Electron transport chain|electron transport chain]] as an [[Electron carrier|electron carrier]] <ref>Alberts et al (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science. Chapter 14, Page 831</ref>. As an electron carrier ubiquinone donates or picks up [[Electrons|electrons]] in redox reactions. Ubiquinone is a small [[Hydrophobic|hydrophobic]] molecule ubiquinone has the ability to move easily through the [[Lipid bilayer|lipid bilayer]] and is not located in a fixed position. 

Ubiquinone, also known as [[Coenzyme_Q|coenzyme Q]], plays an important role in the electron transport chain in mitochondria<ref>Sarah L Molyneux,1,* Joanna M Young,2 Christopher M Florkowski,1,2 Michael Lever,1 and Peter M George1. Coenzyme Q10: Is There a Clinical Role and a Case for Measurement? Clin Biochem Rev. 2008 May; 29(2): 71–82.</ref>. Coenzyme Q transfers electrons from complex I and complex II to complex III in the electron transport chain and is synthesised in all eukaryotic cells<ref>Trends Biochem Sci. 2017 Oct; 42(10): 824–843. Molecular Genetics of Ubiquinone Biosynthesis in Animals. Crit Rev Biochem Mol Biol. 2013 Jan-Feb; 48(1): 69–88.</ref> . Due to the fact that ubiquinone is essential in the production of [[ATP|ATP]], a deficiency in the [[Cofactor|cofactor]] can result in multiple diseases including [[myopathies|myopathies<ref>Jonathan A. Stefely1,2,3 and David J. Pagliarini1,2,*. Biochemistry of Mitochondrial Coenzyme Q Biosynthesis. Trends Biochem Sci. 2017 Oct; 42(10): 824–843.</ref>]].

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James Watson

2018-12-05T12:38:28Z

180143483:

James Watson was a scientist at Cambridge University. He, along with [[Francis Crick|Francis Crick]], proposed the 3-D model and [[Double helix|double helix]] structure of [[Deoxyribonucleic acid|deoxyribonucleic acid ]](DNA). They put forward their theory in 1953<ref>Hartl. D.L. and Ruvolo M. (2012) Genetics: analysis of genes and genomes, 8th edition, United States of America: Jones and Bartlett Learning</ref>. [[Watson-Crick base pairing|Watson-Crick base pairing]] is another name for [[Complementary base pairing|complementary base pairing]] <ref>Hartl. D.L. and Ruvolo M. (2012) Genetics: analysis of genes and genomes, 8th edition, United States of America: Jones and Bartlett Learning</ref>. 

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Anion

2018-12-05T12:36:40Z

180143483: Reference added

An anion is an [[Ion|ion]] with a net negative charge<ref>The Editors of Encyclopaedia Britannica. Anion. 1998 [Cited 5/12/18]; Available from: https://www.britannica.com/science/anion</ref>

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DNA Sequencing

2018-12-05T12:31:40Z

180143483: Reference added

The advent of techniques for the rapid sequencing of [[DNA|DNA]] has led to many major advances in molecular biology. Several methods have now been developed for determining the nucleotide sequence of [[DNA|DNA]], but the [[Sanger “dideoxy” method|Sanger (“dideoxy”) method]] offers significant advantages in terms of rapidity and simplicity of protocol. It is based upon the use of [[Deoxynucleotide analogues|deoxynucleotide analogues]] that are randomly incorporated into a growing [[DNA|DNA]] strand to give specific chain termination<ref>James M. Heather⁎ and Benjamin Chain. The sequence of sequencers: The history of sequencing DNA. Genomics. 2016 Jan; 107(1): 1–8.</ref>.

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Bzip

2018-12-05T12:27:22Z

180143483: Added reference title

Bzip (Basic leucine zipper) is a [[Eukaryotic|eukaryotic]] [[Transcription factor|transcription factor]]. It consists of 2 regions. One basic region which interacts with [[DNA|DNA]], and the 'zipper' region. This region contains a [[Leucine|leucine]] every 7 residues, forming an [[Alpha-helix|alpha-helix]] and is involved in dimerisation. These leucine zipper proteins therefore bind to [[DNA|DNA]] as dimers and grip to the [[Double helix|double helix]]<ref>Alberts B, Bray D, Hopkin K, Johnson A, Lewis J, Raff M, Roberts K, Walter P. Essential Cell Biology. 4th Edition. New York. Garland Science. 2013. p.267</ref>. Members of the bZip family of [[Transcription factors|transcription factors bind]] to target sequences in the [[DNA|DNA]] such as homodimers and heterodimers that recognise [[Palindromic sequence|palindromic sequences]]. This affects developmental processes such as dendritic cell development, myeloid differentiation and brain development<ref>R&amp;D Systems. Basic Leucine Zipper (bZip) Transcription Factors. Available from: https://www.rndsystems.com/research-area/basic-leucine-zipper--bzip--transcription-factorsfckLR Cited: 20/11/17</ref>.

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Non-Coding Rna

2018-12-04T13:51:18Z

180143483: Reference for the information added

Non-coding Ribonucleic acid (ncRNA) is any class of [[RNA|RNA]] that is not [[Translation|translated]] into a [[Polypeptide|polypeptide]]. Non-coding RNAs may act as a biological [[Catalysts|catalysts]], in which case they ae known as [[Ribozymes]]. The [[Spliceosome|spliceosome]] is an example of a piece of biological catalytic machinery that uses ncRNA to catalyse the splicing of pre-[[MRNA|mRNA]]. Another role of ncRNA is the regulation gene control, which can be performed by promoting or inhibiting either [[Transcription|transcription]] or [[Translation|translation]] <ref>Mattick JS1, Makunin IV. Non-coding RNA. Hum Mol Genet. 2006 Apr 15;15 Spec No 1:R17-29.</ref>.

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100,000 genome project

2018-12-04T13:48:46Z

180143483: References added and information about why we sequence the genomes of certain patients in the NHS

The 100,000 genome project is a national project that works to sequence the genomes of 100,000 patients with rare diseases and familial cancers in the NHS. These patients must fit certain eligibility criteria in order to be able to take part in the project. The purpose of the project is to improve treatments for people with cancers and rare diseases by selecting the best treatements; aid diagnosis for people with certain rare diseases and to create a genomic economy<ref>Gabrielle Natalie Samuel and Bobbie Farsides. The UK’s 100,000 Genomes Project: manifesting policymakers’ expectations. New Genet Soc. 2017; 36(4): 336–353.</ref>.

For cancer patients genome sequencing can vastly improve their treatment and prognosis. Scientists will sequence the genome of a healthy cell and of a cancer cell from a patient, allowing the identification of [[Mutations|mutations]] in the [[DNA|DNA]] that may have lead to the development of the cancer. Understanding the cause of the cancer can allow clinicians to select the best treatment plan for the patient and also can give some indication of how the [[Cancer|cancer]] may progress. Genome sequencing is also important for people with rare diseases, as a lot of the time such diseases are undiagnosed and the cause of the disease is unknown. Therefore, understanding the cause of a rare disease on a genetic level can help to diagnose a person and also treat them. As part of the 100,000 genomes project, family members of a patient with a rare disease will also have their genome sequenced due to the fact that such diseases are often [[Inheritance|inherited]] <ref>Genomics England.About Genomics England.Date published unknown.[cited 4/12/18]; Available from: https://www.genomicsengland.co.uk/about-genomics-england/</ref>. 

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Complementary base pairing

2018-11-28T16:01:02Z

180143483: Created page with "Watson and Crick came up with the principle of complementary base pairing when they suggested a structure for DNA <ref>Topal MD, Fresco JR. Complementary bas..."

[[Watson_and_Crick|Watson and Crick]] came up with the principle of complementary base pairing when they suggested a structure for DNA <ref>Topal MD, Fresco JR. Complementary base pairing and the origin of substitution mutations. Nature. 1976 Sep 23;263(5575):285-9.</ref>. The basic principles are that a [[Purine|purine base]] always pairs with a [[Pyrimidines|pyrimidine base]]. In particular adenine will base pair with thymine and form two [[Hydrogen_bonds|hydrogen bonds]] and cytosine will base pair with guanine and form three hydrogen bonds. Base pairing in this way is vital for explaining the mechanisms of DNA replication, transcription, translation and DNA repair <ref>Andrew T. Krueger and Eric T. Kool. Model Systems for Understanding DNA Base Pairing.Published online 2007 Nov 9. doi: [10.1016/j.cbpa.2007.09.019]</ref>. 

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Endonucleases

2018-11-28T15:52:25Z

180143483:

A class of [[Nucleases|nuclease]] which [[Hydrolysis|hydrolyses]] the middle of the [[Polynucleotide Chain|polynucleotide chain]] of a [[Nucleic acids|nucleic acid]]<ref>Alberts B [et al] (2008) Molecular Biology of the Cell, Fifth Edition, New York:Garland Science</ref>, by cleavage of the [[Phosphodiester bond|phosphodiester bond]]. Endonucleases can be non-specific (cleaving indiscriminately along the polynucleotide) or they can be specific, cutting at certain sites which are recognised by the [[Enzyme|enzyme]]; these are called [[Restriction endonucleases|restriction endonucleases]].<ref>Cox M, Nelson DR, Lehninger AL (2005). Lehninger principles of biochemistry. San Francisco: W.H. Freeman. p. 952.</ref>. 

Endonucleases usually recognise [[Palindromic sequence|palnidromic]] sequences in DNA to ensure that both strands of [[DsDNA|dsDNA]] are cleaved<ref>Smith DR1. Restriction endonuclease digestion of DNA. Methods Mol Biol. 1993;18:427-31.</ref>. Some restriction endonuclease enzymes will cut the DNA to give blunt ends, whereas other restriction endonuclease enzymes will cut the DNA to produce sticky ends. The production of [[Sticky ends|sticky ends]] is due to staggered cutting of the DNA sequence. Sticky ends are 5' or 3' overhangs in the DNA sequence. Sticky ends are important in [[Recombinant DNA Technology|recombinant DNA technology]] to allow [[Complementary base pairing|complemetary base pairing]] and [[Hydrogen bonds|hydrogen bonds]] to form between [[Plasmid|plasmid]] DNA and a fragment of DNA<ref>Griffiths AJF, Miller JH, Suzuki DT, et al. An Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000.</ref> 

Restriction endonuclease enzymes are naturally produced by bacteria as a defence mechanism against [[Bacteriophage|bacteriophages]]. The enzyme will cleave viral [[Nucleic acid|nucleic acid]], therefore it can not be transcribed and replicated so no new viral particles can be synthesised inside of the host cell<ref>Griffiths AJF, Miller JH, Suzuki DT, et al.fckLRAn Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000.</ref>. 

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Endonucleases

2018-11-28T15:52:05Z

180143483: Information on sticky ends, natural endonucleases in bacteria and references added

A class of [[Nucleases|nuclease]] which [[Hydrolysis|hydrolyses]] the middle of the [[Polynucleotide Chain|polynucleotide chain]] of a [[Nucleic acids|nucleic acid]]<ref>Alberts B [et al] (2008) Molecular Biology of the Cell, Fifth Edition, New York:Garland Science</ref>, by cleavage of the [[Phosphodiester bond|phosphodiester bond]]. Endonucleases can be non-specific (cleaving indiscriminately along the polynucleotide) or they can be specific, cutting at certain sites which are recognised by the [[Enzyme|enzyme]]; these are called [[Restriction endonucleases|restriction endonucleases]].<ref>Cox M, Nelson DR, Lehninger AL (2005). Lehninger principles of biochemistry. San Francisco: W.H. Freeman. p. 952.</ref>. 

Endonucleases usually recognise [[Palindromic_sequence|palnidromic]] sequences in DNA to ensure that both strands of [[DsDNA|dsDNA]] are cleaved<ref>Smith DR1. Restriction endonuclease digestion of DNA. Methods Mol Biol. 1993;18:427-31.</ref>. Some restriction endonuclease enzymes will cut the DNA to give blunt ends, whereas other restriction endonuclease enzymes will cut the DNA to produce sticky ends. The production of [[Sticky_ends|sticky ends]] is due to staggered cutting of the DNA sequence. Sticky ends are 5' or 3' overhangs in the DNA sequence. Sticky ends are important in [[Recombinant_DNA_Technology|recombinant DNA technology]] to allow[[complementary base pairing |complemetary base pairing]] and [[Hydrogen_bonds|hydrogen bonds]] to form between [[plasmid|plasmid]] DNA and a fragment of DNA<ref>Griffiths AJF, Miller JH, Suzuki DT, et al. An Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000.</ref>

Restriction endonuclease enzymes are naturally produced by bacteria as a defence mechanism against [[Bacteriophage|bacteriophages]]. The enzyme will cleave viral [[Nucleic_acid|nucleic acid]], therefore it can not be transcribed and replicated so no new viral particles can be synthesised inside of the host cell<ref>Griffiths AJF, Miller JH, Suzuki DT, et al.
An Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000.</ref>. 

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Type 1 diabetes

2018-11-27T18:48:21Z

180143483: References and further information added

Type 1 diabetes is an [[Autoimmune disease|autoimmune disease]] where your own body attacks the cells of the [[Pancreas|pancreas]] which produce insulin, it is thought to be [[Inheritance|inherited]], i.e. run in families. This leads to an inability to produce the [[Hormone|hormone]] [[Insulin|insulin]] which is essential for the control of [[Blood glucose level|blood glucose levels]]. [[Insulin|Insulin]] is released from the [[Pancreatic beta cells|beta cells of the islets of langerhans]] in the pancreas, in response to a high glucose concentration, e.g. after eating a meal<ref>Kimber M Simmons and Aaron W Michels. Type 1 diabetes: A predictable disease.World J Diabetes. 2015 Apr 15; 6(3): 380–390.</ref>. This release of [[Insulin|insulin]] causes the [[Liver|liver]] to convert this glucose into [[Glycogen|glycogen]] in the process known as [[Glycogenesis|glycogenesis]] <ref>Rei Noguchi,1 Hiroyuki Kubota,2 Katsuyuki Yugi,2 Yu Toyoshima,2 Yasunori Komori,2 Tomoyoshi Soga,3 and Shinya Kurodaa,1,2,4.The selective control of glycolysis, gluconeogenesis and glycogenesis by temporal insulin patterns. Mol Syst Biol. 2013; 9: 664.</ref>. In a person who doesn't suffer from diabetes, this response is immediate and helps cope with the influx of glucose. This response is vital in maintaining [[Homeostasis|homeostasis]]. However, in a person suffering from type 1 diabetes, this response is not present.

Some of the complications associated with type 1 diabetes include: eye damage, foot damage, kidney damage, cardivascular diseases and complications in pregnancy <ref>Mayo clinic. Type 1 diabetes. 2017 [Cited 27/11/18]. Available from:https://www.mayoclinic.org/diseases-conditions/type-1-diabetes/symptoms-causes/syc-20353011</ref>. Some patients with type 1 diabetes may suffer [[Hypoglycaemia|hypoglycemia]] and [[Hyperglycemia|hyperglycemia]] even when they are being treated with exogenous insulin, although this is a rare, severe form of type 1 diabetes <ref>Health Quality Ontario. Pancreas Islet Transplantation for Patients With Type 1 Diabetes Mellitus: A Clinical Evidence Review. Ont Health Technol Assess Ser. 2015; 15(16): 1–84.</ref>.

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Sterioisomers

2018-11-27T18:22:32Z

180143483: References added and information on racemate mixtures added

Stereoisomers are [[Molecules|molecules]] that have the same [[Molecular formula|molecular formula]], but have a different [[Spatial arrangement|spatial arrangement]]. This means that they are arranged differently in space, despite the fact the [[Atom|atoms]] are bonded in the same order. In order for this to occur, the molecule must contain a [[Carbon|carbon]] that is bonded to four different groups, This is called a [[Chiral centre|chiral centre]], or an [[Asymetric carbon|asymmetric carbon]]. Sterioisomers can be divided into further groups according to the specific spatial arrangements.

== Enantiomers ==

[[Enantiomers|Enantiomers]] are stereoisomers that are non-superimposable mirror images of each other<ref>Naveen Chhabra, Madan L Aseri, and Deepak Padmanabhan1. A review of drug isomerism and its significance.Int J Appl Basic Med Res. 2013 Jan-Jun; 3(1): 16–18.</ref>. They are usually described as having [[D isomer|D]] or [[L isomer|L]] configuration<ref>Sukanya Mitra and Puneet Chopra.Chirality and anaesthetic drugs: A review and an update.Indian J Anaesth. 2011 Nov-Dec; 55(6): 556–562.</ref>. Often one configuration exists more frequently in nature, for example the L form of most [[Amino acid|amino acids]] is more prominant in nature, possibly because they are slightly more soluble than the D form. You can differentiate between the two forms by investigating the direction in which they rotate polarised light.

A racemate mixture contains equal amounts of [[Enantiomers|enantiomers]]<ref>Michael J. Owens, Jonathan McConathy. Stereochemistry in Drug Action.Prim Care Companion J Clin Psychiatry. 2003; 5(2): 70–73.</ref>, therefore racemate mixtures are optically inactive because the enantiomers rotate a plane of polarised light by the same number of degrees in opposite directions<ref>The Editors of Encyclopaedia Britannica.Racemate. 2011. [cited 27/11/18] Available from:https://www.britannica.com/science/racemate</ref>. 

 

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== Diastereoisomers ==

Molecules that have multiple asymmetric carbons are called [[Diastereoisomers|diastereoisomers]]. These are not mirror images of each other. A common example is a [[Monosaccharide|monosaccharide]] that has a carbon chain of three or more, such as [[Glucose|glucose]]. The number of possible stereoisomers is equal to 2n, where n is the number of asymmetric carbons in the molecule. There are two further types of diastereoisomers - [[Epimers|epimers]] and [[Anomers|anomers]]. Epimers are two diastereoisomers that differ at only one of the multiple asymmetric carbons, whereas anomers are cyclic molecules that differ at a new asymmetric carbon that is formed as a result of the ring formation. E-Z or cis-trans isomerism is another type of diastereoisomers, resulting from the restricted rotation around a [[Double bond|double bond]]<ref>Biochemistry, 7th Edition, Jeremy M. Berg, John L. Tymoczko, Lubert Stryer, W. H. Freeman and Company, New York, 2012, chapter 11- page 331, chapter 2 - page 27.</ref>.

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Sterioisomers

2018-11-27T18:22:06Z

180143483: References added

Stereoisomers are [[Molecules|molecules]] that have the same [[Molecular formula|molecular formula]], but have a different [[Spatial arrangement|spatial arrangement]]. This means that they are arranged differently in space, despite the fact the [[Atom|atoms]] are bonded in the same order. In order for this to occur, the molecule must contain a [[Carbon|carbon]] that is bonded to four different groups, This is called a [[Chiral centre|chiral centre]], or an [[Asymetric carbon|asymmetric carbon]]. Sterioisomers can be divided into further groups according to the specific spatial arrangements.

== Enantiomers ==

[[Enantiomers|Enantiomers]] are stereoisomers that are non-superimposable mirror images of each other<ref>Naveen Chhabra, Madan L Aseri, and Deepak Padmanabhan1. A review of drug isomerism and its significance.Int J Appl Basic Med Res. 2013 Jan-Jun; 3(1): 16–18.</ref>. They are usually described as having [[D isomer|D]] or [[L isomer|L]] configuration<ref>Sukanya Mitra and Puneet Chopra.Chirality and anaesthetic drugs: A review and an update.Indian J Anaesth. 2011 Nov-Dec; 55(6): 556–562.</ref>. Often one configuration exists more frequently in nature, for example the L form of most [[Amino acid|amino acids]] is more prominant in nature, possibly because they are slightly more soluble than the D form. You can differentiate between the two forms by investigating the direction in which they rotate polarised light.

A racemate mixture contains equal amounts of [[Enantiomers|enantiomers]]<ref>Michael J. Owens, Jonathan McConathy. Stereochemistry in Drug Action.Prim Care Companion J Clin Psychiatry. 2003; 5(2): 70–73.</ref>, therefore racemate mixtures are optically inactive because the enantiomers rotate a plane of polarised light by the same number of degrees in opposite directions<ref>The Editors of Encyclopaedia Britannica.Racemate. 2011. [cited 27/11/18] Available from:https://www.britannica.com/science/racemate</ref>. 

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== Diastereoisomers ==

Molecules that have multiple asymmetric carbons are called [[Diastereoisomers|diastereoisomers]]. These are not mirror images of each other. A common example is a [[Monosaccharide|monosaccharide]] that has a carbon chain of three or more, such as [[Glucose|glucose]]. The number of possible stereoisomers is equal to 2n, where n is the number of asymmetric carbons in the molecule. There are two further types of diastereoisomers - [[Epimers|epimers]] and [[Anomers|anomers]]. Epimers are two diastereoisomers that differ at only one of the multiple asymmetric carbons, whereas anomers are cyclic molecules that differ at a new asymmetric carbon that is formed as a result of the ring formation. E-Z or cis-trans isomerism is another type of diastereoisomers, resulting from the restricted rotation around a [[Double bond|double bond]]<ref>Biochemistry, 7th Edition, Jeremy M. Berg, John L. Tymoczko, Lubert Stryer, W. H. Freeman and Company, New York, 2012, chapter 11- page 331, chapter 2 - page 27.</ref>.

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