BIOL 3510 1st Edition Lecture 5 Outline of Last Lecture I. Nucleotides and the Composition of DNAII. GenomeIII. Chromosome packingIV. Inside of the Nuclear EnvelopeOutline of Current Lecture I. Intro to TranscriptionII. Types of RNAIII. Bacterial TranscriptionIV. Eukaryotic TranscriptionCurrent LectureThe Central Dogma Differences between RNA and DNA-Nucleotide sugar is ribose-Uses uracil instead of thymine-Typically single stranded RNA molecules can fold into specific 3D shapes that have catalytic and structural functions. Transcription produces an RNA molecule that is complementary to the template strand of DNA. Polymerases catalyze the formation of phosphodiester bonds. RNA polymerases mediate transcription. Genes are transcribed by many RNA polymerases at the same time. Types of RNA Produced in CellsType of RNA FunctionMessenger RNAs (mRNAs) Code for proteinsRibosomal RNAs (rRNAs) Form the core of the ribosomes structure and catalyze protein synthesismicroRNAs (miRNAs) Regulate gene expressionThese 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.transferRNAs (tRNAs) Serve as adaptors between mRNA and amino acids during protein synthesisOther noncoding RNAs Used in RNA splicing, gene regulation, telomere maintenance, and many other processes Bacterial Transcription -The sigma factor subunit of RNA polymerase recognizes the promoter-The DNA is unwound and transcription begins Specific sequences tell bacterial RNA polymerase where to start (promoter) and stop (terminator) transcription. Eukaryotic transcription differs from prokaryotic transcription. Three types of RNA polymerases transcribe different types of genes.Type of Polymerase Genes TranscribedRNA polymerase I Most RNA genesRNA polymerase II All proteins including genes, mRNA genes, plus genes for other noncoding RNAs (e.g. those in spicesosomes)RNA polymerase III tRNA gene5S rRNA geneGenes for many other small RNAs Transcription factors are needed to initiate transcriptionInitiation requires dealing with nucleosomes Eukaryotic transcription General transcription factors are required for RNA pol II initiation-TFIID = TPD + 11 TAF subunitsThe TBP subunit of TFIID distorts the DNA double helix-TFIIB recognizes the distorted DNATFIIF - stabilizes interaction between RNA pol II & TFIID/BTFIIE - recruits TFIIHTFIIH - unwinds DNA at start site, phosphorylates RNA pol II CTDAfter phophorylation, RNA pol II disassociates from the Tfs and enters elongation phase Eukaryotic RNAs are processed prior to export from the nucleus mRNAs are capped and polyadenylated The coding regions (exons) of eukaryotic genes are interrupted by intronsSplicing removes the introns and is mediated splicesomes. Splicesomes: consist of multiple small nuclear ribonucleoproteins (snRNPs) which contain small nuclear RNAs (snRNAs) and proteins; recognize specific RNA sequences Proteins initially bound to RNA pol II mediate RNA processing Alternative splicing increases protein diversity Only properly processed mRNAs are exported from the nucleus to the cytoplasm. Proteins that recognizethe mRNA modifications bind to the RNA and interact with the nuclear pore complex to allow
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