Biology 151 1st Edition Lecture 13 Outline of Last Lecture 1. Transcription by RNA polymerase2. What's the code? DNA sequence contains code for linking amino acids into protein3. At ribosome4. Is it a nucleic acid?5. How do you bind all 64 codons?6. Summary - the roles of RNA in translation7. Starting and stopping translation: Starting translation in correct reading frame8. Stopping translation9. mRNA can have 5' and 3' un-translated regions10. In prokaryotes one mRNA can code for several different proteinsOutline of Current Lecture 1. Starting and stopping transcription from region of DNA - the transcription unit:2. Controlling transcription of RNA from DNA3. "General" transcription factors4. mRNA processing in eukaryotes5. Sliceosome6. Non-coding transcription units7. Example: eukaryotic rRNA genesCurrent Lecture - 2/18/15Starting and stopping transcription from region of DNA - the transcription unit:- specific nucleotides can act as docking sites for specific proteins- promoter DNA: where RNA polymerase binds and transcription starts- terminator DNA: where transcription stops - these are not codons- different "transcription units" = regions of DNA transcribed into mRNAControlling transcription of RNA from DNA:- location or use of promoter by RNA polymerase controlled by whether protein transcription factors bind to nearby DNA- transcription factor proteins can recognize specific nucleotides, promote or inhibit transcription"General" transcription factors:- used by most genes to help RNA polymerase recognize and bind to promoter nucleotides - 1 in bacteria- several in eukaryotes- TATA box = promotermRNA processing in eukaryotes:- 1) 5' and 3' ends modified -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.-capping of 5' mRNA by special nucleotide-3' end cleaved and long stretch of about 250 A's (poly-A-tail) added to 3' endhelps export RNA from nucleus, stabilize RNA attach RNA to ribosome- 2) removal of non-codon --DNA and primary RNA often contains regions not present in mature mRNA-removed parts = introns-parts that remain = extronsSpliceosomes:- proteins and nuclear RNAs (snRNAs), removes introns - sRNAs bind, recognize specific nucleotides at exon-intron junctions- sRNAs also help splice ribozymes- only a small percentage of eukaryotic DNA contains protein-coding exons- thicker = exons- thinner = introns- some eukaryotic mRNAs use alternative splicing to keep different exons - get different mRNAs, proteins- transcription starts at promoter- translation starts at start codon- promoter is recognized by general transcription factors - intron-exon splice sites are recognized by snRNAs - info. for nucleotides in snRNAs comes from DNANon-coding transcription units:- some RNA transcripts from DNA are not mRNAs - not made into proteins at ribosomes- ex. tRNA, rRNA, snRNA, others- do not have 5' caps, polyAtails- often made by different RNA polymeraseExample: eukaryotic rRNA genes:- one transcription unit for 3 of the 4 RNAs, spliced and cut into 3 rRNAs- 100s of copies of gene in cluster in DNA- transcription, processing and assembly in nucleolus- controlling = "gene expression"- most cells in organism contain the same DNA - not all cells make ("express) functional proteins from
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