{"id":679,"date":"2014-04-30T12:47:44","date_gmt":"2014-04-30T12:47:44","guid":{"rendered":"http:\/\/hyndland-sec-glasgow.blogs.rm.com\/CfE-Higher-Unit-1\/?page_id=25"},"modified":"2014-04-30T12:47:44","modified_gmt":"2014-04-30T12:47:44","slug":"one-gene-many-proteins","status":"publish","type":"page","link":"https:\/\/blogs.glowscotland.org.uk\/gc\/hyndsecbiohu1\/one-gene-many-proteins\/","title":{"rendered":"One gene many proteins"},"content":{"rendered":"
(e) Different proteins can be expressed from one gene as a result of alternative RNA splicing and post-translational modification. Different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and introns.<\/span>
\n Post translation protein structure modification by cutting and combining polypeptide chains or by adding phosphate or carbohydrate groups to the protein.<\/span><\/h5>\n\n\n\n
\"PPt\"<\/a><\/td>\n\"HwrkRevisionIcon\"<\/a><\/td>\n\"MCQIcon\"<\/a><\/td>\n\"MCQIcon\"<\/a><\/td>\n\"MCQIcon\"<\/a><\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Homework Sheets 1_5<\/a>\/ 1_5A<\/a>, 1_5B<\/a><\/p>\n

source:\u00a0RNA Splicing: Introns, Exons and Spliceosome\u00a0 By: Suzanne Clancy, Ph.D. \u00a9 2008 Nature Education<\/a><\/h6>\n

It is now becoming clear that the number of genes present in cells is fewer than the number of proteins which those cells can produce. \u00a0This is as a result of some genes being capable of producing more than one protein product. \u00a0There are two processes which contribute to the production of more than one protein. \u00a0Post transcriptional processes (alternative RNA splicing) and post translational modification.<\/p>\n

Alternative RNA splicing<\/h2>\n

For most eukaryotic genes (and some prokaryotic ones), the initial RNA that is transcribed from a gene’s DNA template must be processed before it becomes a mature messenger RNA (mRNA) that can direct the synthesis of protein.\u00a0\u00a0 In this way, the primary mRNA<\/strong>\u00a0transcript becomes the mature mRNA transcript.\u00a0<\/strong> This process is known as splicing<\/strong>.
\nRNA splicing involves the removal or “splicing out” of certain sequences in the mRNA, referred to as intervening sequences, or introns<\/strong>.\u00a0 The final or mature mRNA thus consists of the remaining sequences, called exons<\/strong>, which are connected to one another during the splicing process.
\nSplicing different combinations of exon<\/strong> together can lead to the production of a variety of different proteins being produced from a single gene. \u00a0In the diagram below, three different proteins have been produced from the same gene, as a result of combining different exons together.<\/p>\n

\"DNA_alternative_splicing_FULL\"<\/a><\/p>\n

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Examples of genes where alternative splicing leads to the production of different protein products include the gene CGRP (Calcitonin Gene Related Peptide), which can produce either CGRP or calcitonin depending on what splicing activity occurs. \u00a0Typically CGRP, a neurotransmitter, is the product found in neurones and calcitonin, a hormone conerned with regulation of calcium levels in the blood is produced in non-neuronal cells such as the thyroid gland.<\/p>\n

\"figure_29_41\"<\/a><\/p>\n

\u00a0Post Translational Processing<\/h2>\n

In addition to differences between the mRNA transcripts exported to the ribosome, the protein produced by the ribosome can become modified following synthesis. \u00a0Modifications can include proteolytic cleavage (enzymes break the protein into smaller, functional fragments), or the addition of various other molecules including sugars (known as glycosylation) or phosphate groups (phosphorylation).<\/p>\n

Cleavage<\/p>\n

The gene known as the POMC (pro-opio melanocortin) gene \u00a0encodes a 285-amino acid polypeptide hormone precursor that is processed by enzymatic cleavage to produce a range of protein products. \u00a0The protein produced is tissue specific and each has a different function within the body including \u00a0roles in pain, regulating metabolic rate, \u00a0pigmentation<\/a> and immune function.<\/p>\n

\"pomc1334541252805\"<\/a><\/p>\n

Glycosylation<\/p>\n

A number of proteins including mucus and cell – cell adhesion moleules and cell-cell recognition molecules are glycosylated after synthesis.\u00a0 Glycosylation is required for the correct functioning of these molecules, and\u00a0a number of\u00a0conditions, occurring as a result of disorders of glycosylation have been identified.<\/p>\n

Phosphorylation<\/p>\n

Regulation of proteins by phosphorylation is a very common method of\u00a0regulation of cell function.\u00a0 the protein switches between a phosphorylated and an unphosphorylated form, and one of\u00a0which is active,\u00a0the other one\u00a0inactive.\u00a0 The phosphates groups are added and removed by enzymes (kinase and phosphatases respectiviely).\u00a0 The importance of phosphorylation is illustrated by p53, a tumour suppressor protein which stops cell division.\u00a0 A number of\u00a0cell changes, including DNA damage\u00a0cause the protein to\u00a0become phopshorylated, which causes it to become active.\u00a0 Active p53 protein then instructs the cell to respone appropriately to the damge intis DNA, this could be repairing the damage of even causing programmed cell death (apopotosis).<\/p>\n

For some people, the gene encoding p53 can become damaged by mutation or they can inherit a faulty version.\u00a0 In such cases, p53 protein is inactive and these individuals are more likely to develop some types of cancer.\u00a0 The human papilloma virus, associated with the development\u00a0of cervical cancer produces a protein which inactivates p53.<\/p>\n

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(e) Different proteins can be expressed from one gene as a result of alternative RNA splicing and post-translational modification. Different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and introns. Post translation protein structure modification by cutting and combining polypeptide chains or by adding phosphate … Continue reading “One gene many proteins”<\/span><\/a><\/p>\n","protected":false},"author":2454,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"open","template":"","meta":{"footnotes":""},"class_list":["post-679","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/blogs.glowscotland.org.uk\/gc\/hyndsecbiohu1\/wp-json\/wp\/v2\/pages\/679","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.glowscotland.org.uk\/gc\/hyndsecbiohu1\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/blogs.glowscotland.org.uk\/gc\/hyndsecbiohu1\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.glowscotland.org.uk\/gc\/hyndsecbiohu1\/wp-json\/wp\/v2\/users\/2454"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.glowscotland.org.uk\/gc\/hyndsecbiohu1\/wp-json\/wp\/v2\/comments?post=679"}],"version-history":[{"count":0,"href":"https:\/\/blogs.glowscotland.org.uk\/gc\/hyndsecbiohu1\/wp-json\/wp\/v2\/pages\/679\/revisions"}],"wp:attachment":[{"href":"https:\/\/blogs.glowscotland.org.uk\/gc\/hyndsecbiohu1\/wp-json\/wp\/v2\/media?parent=679"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}