Unformatted text preview:

Essential Elements of Biochemistry BCHM 3050 Dr Srikripa Chandrasekaran Lecture 2 16 15 Notes Transcription Continued I II III IV V Termination of transcription A Don t need a helicase to start transcription but you need a helicase to terminate transcription Transcription of eukaryotes A One strand serves as a template to make mRNA it goes 5 3 B Eukaryotes have 3 RNA polymerases that all have their own specific C functions prokaryotes only have 1 RNA polymerase In eukaryotes RNA polymerase cannot initiate transcription they need initiation factors or transcription factors D In eukaryotes have enhancers and silencers that modify transcription E Once mRNA is made in eukaryotes there are a lot of edits that are made to it this editing process does not occur in prokaryotes In the nucleolus ribosomal RNAs are made rRNA 1 is made here Eukaryotic RNA polymerases A 3 different polymerases differ in location and function B C Nucleolus is the dense areas in the nucleus that makes rRNAs Features of eukaryotic promoters A Every promoter has a TATA box every gene has a TATA box B The TATA box is at 25 bases from the start sight in the promoter region of eukaryotes C TATA box is mandatory depending on the type of gene one or some of the other boxes may be needed as well D The TATA boxes are in similar positions in the same genes from organism to organism E A strong promoter allows many copies to be made F TATA box is universal and highly conserved across eukaryotes G CAAT box strong promoter Initiation of eukaryotic transcription A TF transcription factor B Many transcription factors bind to the TATA box C The order of the transcription factors is different in different genes D TFs first come to the promoter E TFIIH very important Across all organisms TFIIH phosphorylates RNA polymerase II and this is critical for eukaryote transcription puts phosphate group onto RNA polymerase II and activates it VI Enhancers A An enhancer region is a region in DNA that lives about 1 000 2 000 base pairs up stream or before the promoter B An activator binds to the enhancer 1 E rRNA must be taken up to ribosomes VIII mRNA processing in eukaryotes VII IX X C An activator is a protein D When the activator binds to the enhancer it bends or loops the DNA and activates RNA polymerase E RNA polymerase II carries out transcription but it needs the help of an activator the activator helps the RNA polymerase II to transcribe the DNA the lack of an activator can lead to diseases because the transcription process will be very poor RNA processing A The making of any RNA is called transcription making mRNA rRNA or tRNA is all called transcription In eukaryotes RNA processing occurs B 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 a tRNA it does not come decorated with amino acids until later when it is modified and the amino acids are added A 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 In order to produce a mature mRNA it must go through 5 capping 3 polyadenylation and splicing B C Prokaryotic mRNA s do not require processing The 5 cap of eukaryotic mRNA A mRNA is a single strand of nucleotides bonded by phosphodiester bonds end of the DNA B Capping adding a whole extra unit to the 5 end of the chain C Methylate quanosine at the 7 carbon position and attached to the 5 D Heavy methylate 5 end and add 7 methyl guanosine E Be able to determine what a 5 cap looks like on the exam F DNA calls the shots but it cannot maneuver out of the nucleus so mRNA takes order from the DNA and hen leaves the nucleus to transfer the information G 5 cap helps the mRNA to be seen by the ribosome H The 5 cap is a recognition site to get the mRNA to the ribosome I The mRNA needs to be protected once it leaves the nucleus J Exonucleoses chew away the MRNA but they cannot work when the 5 cap is present so the 5 cap protects the mRNA and prolongs its life K The 5 cap is 7 methyl guanosine mRNA polyadenylation A At the 3 end the poly A tail is added B 5 cap is added to the 5 end C Poly A polymerase is the enzyme that adds the poly A tail to the 3 end of the RNA strand via the process of polyadenylation by 2 XI D The poly A tail prevents degradation of the mRNA E Both the 5 cap and the poly A tail prevent degradation of the mRNA F The poly A tail guides the mRNA out of the nucleus and prevents degradation mRNA splicing A The body of the gene should only be made of exons so in order to achieve this mRNA splicing occurs in which the introns are cut out B Mechanism of mRNA splicing snRNPs and splicesomes 1 Spliceosome complex is a bag of enzymes that will cut out introns and stich together the exons 2 snRNP attached to the junction between the exon and the intron recruits the protein part enzyme to that region splicing 3 Spliceosome mix of snRNP and proteins ribonucleo proteins that cut out the introns An intron is called a lariat when cut out XII Possible functions of introns A We do not really know the function of introns B One possible reason is that they may help in the process of exon shuffling bot not all proteins shuffle exons 3


View Full Document

Clemson BCHM 3050 - Transcription

Documents in this Course
Exam 1

Exam 1

6 pages

Exam 1

Exam 1

9 pages

Load more
Download Transcription
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Transcription and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Transcription 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?