Chapter18.pdf BIOLOGY 108 - 0001
Popular in General Biology I
Popular in Biology
This 3 page Class Notes was uploaded by Koral Shah on Friday November 13, 2015. The Class Notes belongs to BIOLOGY 108 - 0001 at University of Missouri - Kansas City taught by Marilyn Yoder in Fall 2015. Since its upload, it has received 26 views. For similar materials see General Biology I in Biology at University of Missouri - Kansas City.
Reviews for Chapter18.pdf
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 11/13/15
AP Biology 20122013 Unit 8 Chapter 18 Regulation of Gene Expression 181 Transcription Regulation Operator DNA segment on which repressor will bind to turn operon off or on Repressor binds to the operator to block RNA polymerase from binding and transcribing DNA Regulatory Gene makes up the repressor in order to regulate enzyme activity ex trp or allactose Repressible Operon transcription is usually on but it can be inhibited ex trp operon Inducible Operon usually off but can be stimulated ex lac operon when lactose is present operon will be turned on to synthesize lactose digesting enzymes Both trp and lac operon regulation is NEGATIVE feedback both are turning their operons off from their natural state Cyclic AMP CAMP accumulates when glucose is scarce interacts with a regulatory protein called an Activator that will bind to DNA to stimulate transcription of a gene example of positive feedback CAP catabolite activator protein a particular Activator increases affinity of RNA polymerase for the promoter increasing rate of transcription this controls not only whether the operon is on or off but the intensity of it as well think of it as volume Duel Regulation when lactose represses the repressor Corepressor Vs Inducer Inducer inactivates repressor to activate the operon ex Allactose in lac operon Corepressor binds to the repressor to turn off the operon ex Trp 182 Eukaryotic Gene Expression Differential Gene Expression expression of different genes by cells with the same genome almost all humane cells have an identical genome but differentiate depending on what genes they express exception immune system cells they do not have an identical genome Histone Acetylation acetyl groups added to histone tails neutralize charge and loosen chromatin encourages transcription turning on the gene DNA Methylation addition of methyl group to Cytosine nucleotide condenses chromatin suppresses transcription discouraging transcription silencing a gene Epigenetic Inheritance inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence DNA is not permanently changed ex modifications to chromatin can be reversed may explain why identical twins can acquire different genetically based diseases Control Elements segments of noncoding DNA that serve as binding sites for transcription factors which regulate transcription Transcription Factors helpers necessary in order to initiate transcription ex TATA Box a general transcription factor essential for transcription of ALL genes Activators Promoter DNA k r Gene LVJ k v J Enhancer Istal control TATA element box General transcription J39 quot39 39a factors quot gDNAbending 3 3 lI protein f I39 quot Group of mediator proteins 39 RNA polymerase II polymerase II Transcription initiation complex RNA Synthes39s Repressors can also bind to control elements in order to inhibit gene expression blocking the activator Enhancers more distant from the promoter distal control elements on Which activators bind controls the rate of gene expression Eukaryotic Gene Expression ControlCoordinate Regulation typically scattered over different chromosomes analogy raised ags on a few mailboxes dispersed through a neighborhood signaling the mail carrier to check those boxes activators mail carriers recognize the control element signals mailbox ags and bind to them this promotes simultaneous transcription of the various involved genes regardless of placement in the genome occur in response to chemical signals outside the cell hormones and growth factors Alternative RNA Splicing different segments of RNA can be treated as exons an introns creates variation of proteins synthesized from the same strand of RNA mRNA Degradation can regulate gene expression Initiation stage of translation can regulate gene expression initiation can be blocked at poly A tail or Gcap by regulatory proteins preventing attachment to ribosomes Protein Processing Regulation posttranslation When proteins are being processed any step can be inhibited in order to regulate expression selective degradation proteins Will be marked With a ubiquitin protein that signals the need for degradation proteasomes protein complexes that recognize the ubiquitintagged proteins and degrade them 183 Noncoding RNA39s RNA Interface RNAi way for cells to degrade mRNA to adapt to the environment exploits mRNA that mimics viral or foreign DNA so the RNAi policeman will karate chop it away and silence the gene 185 Cancer Oncogenes cancercausing genes found in certain types of Viruses ProtoOncogenes normal cellular genes that cause for proteins that cause normal cell growth How do protooncogenes become oncogenes Mutations that cause protooncogenes to grow and divide at an abnormal rate Three Main Causes movement of DNA within the genome to the promoter causing easy and fast transcription amplification of a protooncogene gene is duplicated far too much point mutations in a control element causing increase in expression point mutations in a protooncogene makes protein resistant to degradation or more active TumorSuppressor Genes encode for proteins that inhibit the cell cycle prevents damaged mutated DNA from being passed down allows for proper cell anchorage if inhibited cell growth is promoted in the absence of suppression Ras Gene relays a signal from a growth factor to begin a cascade of phosphorylation ultimately causing cell division when Ras is mutated no growth factor is needed to promote the cascade so cell division is being stimulated even though there is already an accumulation of cells p53 Gene tumor suppressor gene encodes for a transcription factor that inhibits the cell cycle when p53 is mutated the gene is knocked out causing excessive cell division Heterochromatin more condensed chromatin Euchromatin less condensed chromatin