Essential Elements of Biochemistry BCHM 3050 Dr Srikripa Chandrasekaran Lecture 3 23 15 Notes The Genetic Code Protein Synthesis continued I II Some antibiotics act by blocking transcription or translation A A lot of antibiotics against prokaryotes bacteria block translation B Tetracycline only works on prokaryotes not eukaryotes C Chloramphenicol blocks the peptidyl transferase reaction on ribosomes peptidyl transferase catalyzes the peptide bond between the 2 aminoacytyl A D Cordycepin blocks messengered RNA works against translation fungus in caterpillar RNA Polymerase II E Alpha Amanitin blocks transcription ONLY in eukaryotes binds to Alpha Amanitin A You want to avoid consuming this mushroom because of its toxins B Some mushrooms are edible while others are very toxin and can cause death 1 Regulation of Transcription continued I Epigenetic regulation example A B IGF2 and and H19 are both involved in growth In the mom the IGF2 does not work and is not expressed so offspring rely on their dad s IGF3 C Across all human beings the maternal IGF2 is silenced and the paternal H19 is silenced D Offspring rely on mom s H19 and dad s IGF2 E If the mom s H19 is bad or mutated and since the dad s H19 is epigenetically silenced from the beginning then the offspring does not express H19 and this is called Angelman Syndrome If the dad s IGF2 is bad or mutated and since the mom s IGF2 is epigenetically silenced from the beginning then the offspring does not express IGF2 and this is called Prader Willi Syndrome F G Angelman Syndrome and Prader Willi Syndrome have very similar symptoms neither syndromes are gender based H IGF2 and H19 are located on the same chromosome I Females and males produce the same amount of proteins from the X chromosomes because 1 of the female s X chromosome is epigenetically silenced covered this is gender based II LCR Locus Control Region Example of enhancer region in eukaryotes A This disease is as common as cystic fibrosis B This is a recessive mutation so people with at least one dominant III IV V gene is protected C The survival rate of this disease is very low D Beta subunit of hemoglobin is dysfunctional E LCR Locus Control Region enhancer F A mutation in the LCR off the globin gene creates Beta Thalessemia Specific transcription factors repressors A Activators can bind to enhancers and allow transcription B In eukaryotes the repressors bind to silencers and this prevents transcription negative regulator Post transcriptional regulation A Any changes in the histones DNA enhancers activators etc falls under transcriptional control RNA processing alternative RNA splicing A Alternative RNA splicing makes one huge mRNA that comes with the introns for both removes specific introns depending upon which mRNA is being made different mRNAs make different proteins both mRNAs are different but they come from the same source or same DNA this reduces the energy cost of the process examples of a post transcriptional process VI mRNA degradation A miRNA are normally produced in our body 2 B miRNA have some sequence similarities with mRNA C siRNA small interfereing RNA D miRNA micro RNA E Whenever the cell does not want the mRNA to be converted in a protein then the miRNA sticks to the mRNA F miRNA and siRNA are made in our body and always floating around whenever the body needs to block an mRNA one goes to stick to the mRNA and they either degrade it or block translation machinery from attaching to it Operons A The enhancer is really far away from the promoter and start of the gene so operons are often used B Operons have one regulatory unit for multiple genes Four types motifs of DNA binding regulatory proteins A Example of a DNA binding protein repressors activators RNA polymerases histones B Most DNA binding proteins have these 4 motifs Helix Turn Helix 1 2 Zinc Fingers 3 Leucine Zippers 4 Helix Loop Helix If a protein has any of these motifs then it can probably bind DNA C Transcription factors have DNA binding and activation domains A Transcription activator has an activation domain B DNA binding proteins need weak interactions like hydrogen interactions but NEVER covalent bonds because the protein eventually needs to let go C Activation domain is rich in acidic amino acid residues DNA protein binding can have positive or negative effects A Positive regulation allows transcription carried out by activators genes are turned on B Negative regulation prevents transcription carried out by repressors genes are turned off The lac operon A For the lac operon transcription is stimulated in the presence of lactose B Transcription in bacteria is usually stimulated by glucose but it can also be stimulated by lactose Glucose vs Lactose A Glucose is a 6 member ring B Lactose is 2 rings together a glycosidic bond holds the 2 rings together lactose has 2 sugars C Allo Lactose is an isomeric form of lactose Lactose breakdown A Some lactose is converted into Allo Lactose which is not broken down B The rest of lactose gets broken down into galactose and glucose VII VIII IX X XI XII XIII 3 XIV C In the beginning eukaryotes were not able to digest lactose but over time we adapted to be able to break it down D Individuals who are lactose intolerant cannot break down lactose PROG A PROG all operons are arranged in this manner P promoter R repressor O operator G all the genes that are regulated by this operon B Have operator in prokaryotes but not in eukaryotes C Repressor is constantly being made in bacteria D Repressor binds to the operator usually this causes the operon to be off and the genes cannot be made E The operon is constantly off in bacteria and it gets turned on in special conditions XV XVI Structure of the lac operon A Z Y and A are the genes Repression of the lac operon A The repressor protein is constantly being made and the lac operon is XVII The lac repressor off motif A This particular repressor for the lac operon has a helix turn helix B The helices are what bind to the DNA XVIII De repression activation of the lac operon A When lactose is present in the medium and the bacteria does not have glucose then the allo lactose can bind to the repressor and remove it from the operator so that the operon can turn on B Galactosidase permease and transacetylase are the enzymes that are needed to help break down lactose 1 Permease helps to get lactose into the cell 2 Galactosidase helps to break down lactose 3 Transacetylase helps to convert lactose to glucose so that it can be
View Full Document
Unlocking...