BCHM 3050 1st Edition Lecture 22 Outline of Last Lecture I One gene One enzyme II Transcription III Promoters and Consensus Sequences IV E Coli RNA Polymerase V Initiation and Elongation Stages of Transcription in Prokaryotes VI Active Genes are Transcribed Many Times VII The Role of Rho Factor Outline of Current Lecture I Transcription in Eukaryotes II Eukaryotic RNA Polymerases III Eukaryotic Promoters IV Initiation of Eukaryotic Transcription V Enhancers VI RNA Processing VII 5 Cap of Eukaryotic mRNA VIII mRNA Polyadenylation IX mRNA Splicing Current Lecture I II III Transcription in Eukaryotes a Eukaryotes have 3 RNA polymerases with all of their own functions b RNA polymerase cannot initiate transcription without initiation factors or transcription factors in eukaryotes c Enhancers and silencers are also present to modify transcription d Many modifications edits happen to mRNA once it is made in eukaryotes unlike prokaryotes Eukaryotic RNA Polymerases a 3 different polymerases differ in location and function b Nucleolus is the dense area in the nucleus that makes rRNAs location of RNA polymerase 1 c Polymerase 2 mRNA d Polymerase 3 tRNA Eukaryotic Promoters These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute IV V VI VII a TATA box is at 25 bases from the start sight in the promoter region of eukaryotes ALL eukaryote genes have this b Do not need to know the positions of the CAAT box GC box etc because their presence varies from gene to gene i TATA box is universal and highly conserved across eukaryotes c CAAT box strong promoter that allows the gene to make many many amount of the gene d GC box housekeeping gene Initiation of Eukaryotic Transcription a TF transcription factor b Do not need to know the order that the transcription factors come in because they vary from gene to gene c TFIIH phosphorylates the RNA polymerase puts phosphate group onto RNA polymerase II and activates it which is critical for eukaryotes to carry out transcription Know This d Location of TATA box 25 Enhancers a Enhancer lives 1 000 2 000 bp upstream of the promoter usually sometimes lives downstream of the promoter but this is very rare b Transcription activators are proteins that bind to the enhancer activators bend loops the DNA and attaches to RNA polymerase II c Activators helps RNA polymerase II to transcribe DNA d Diseases can result if this does not happen e Enhancer is part of the DNA sequence f Activator is a protein that binds to RNA polymerase II RNA Processing a Making of any type of RNA is known as transcription b Only mRNA goes through translation and makes proteins c Premature RNAs are made first which then go through RNA processing to be modified and create the final RNA product d When you make an tRNA it doesn t come decorated with amino acids until later when it is modified e rRNA must be taken to the ribosomes in order to carry out its function f Gene is part of a double stranded DNA RNA polymerase bound to sense strand Initiation factors TATA box bind to promoter recruit RNA polymerase activator bound to enhancer activate RNA polymerase II expand DNA molecule mRNA processing 5 Cap of Eukaryotic mRNA a mRNA is a single strand of nucleotides bonded by phosphodiester bonds b Capping adding a whole extra unit to the 5 end of the chain VIII IX c Methylate guanosine at the 7 carbon position and attached to the 5 end of the DNA d Heavily methylate 5 end and add 7 mehtyl guanosine e Be able to determine what a 5 cap looks like on the exam f DNA is only in the nucleus so mRNA takes orders from the DNA and then leave the nucleus to carry the information g 5 cap helps the mRNA to be seen by the ribosome h 5 cap is a recognition site to get the mRNA into the ribosome and prevents digestion degradation of mRNA by exonucleases i Exonucleases chew away the mRNA but they cannot work when 5 cap is present mRNA Polyadenylation a 5 cap is added to the 5 end b Poly A tail is added to the 3 end of the RNA strand via the process of polyadenylation by Poly A polymerase c Poly A polymerase added the Poly A tail d Functions of Poly A tail Guides mRNA out of the nucleus and prevents degradation of the mRNA e Both the cap and the tail aid in preventing degradation mRNA Splicing a The body of the gene should only be made of exons so in order to achieve this mRNA splicing excises introns out and stiches exons together b Splicing the process of removing the introns c Spliceosome complex bag of enzymes that will cut out introns and stitch together the exons d snRNA attatches to the junction between the exon and the intron recruits the protein part enzyme to that region splicing e Spliceosome mix of snRNA and proteins ribonucleo protein that cut out the intron i Intron is called a lariat when cut out
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