BSC 160 1nd Edition Lecture 12 Outline of Last Lecture 1 Endocytosis 2 Mitochondria 3 Endosymbiosis 4 Central Dogma Outline of Current Lecture 1 Transcription 2 Sigma Factor 3 Regulation of Protein Synthesis Metabolism 4 Translation Current Lecture Transcription Use DNA as template make RNA No T s in RNA there are U s 10 35 Distance from first nucleotide that needs to be transcribed Sigma factor Only prokaryotes have this Bacterial What recognizes the 10 35 to align the polymerase to bind To synthesize transcript 3 Steps of Transcription 1 Initial Opens up DNA starts copy from template strand 2 Elongation Finish copying 3 Terminate Ending of copying Don t want to go beyond site of transcription One transcript for each gene ONLY in eukaryotes One gene One messenger RNA Polycistronic Only Prokaryotes multiple genes in same transcriptional region Promoters site P Real terminator site t Operon series of genes tightly controlled with some related function What determines amount of RNA 1 How often do you initiate transcription More frequent more there are 2 How fast is your polymerase 3 Strong promoters Transcribed often Binds tightly to sigma factor Weak promoters Less transcription 4 Repressors Enhancers Turn on and off Repressors Block promoters stop transcription Enhancers CAP helps RNA polymerase bind correctly to transcription location Regulation of Protein Synthesis Metabolism Genes are regulated to be active only when their products are required In prokaryotes this regulation is coordinated by operons a set of genes all of which are regulated as a single unit Lactose Operon Inducible Operon Normally off position Arginine Operon Repressible Always on position Enterons Only eukaryotes Extra DNA Translation Each triplet of nucleotides on the RNA specifies a particular amino acid A protein s structure determines its shape function Proteins determine phenotype Living things are what their proteins make them DNA is mainly a blueprint that tells the cell which kinds of protein Messenger RNA mRNA Carries DNA message through complimentary copy message is in triplets called codons Transfer RNA tRNA Secondary structure creates loops bottom loop exposes a triplet of nucleotides called anticodon which designates amino acid complement mRNA carries specific amino acid to ribosomes Ribosomal RNA rRNA Component of ribosomes where protein synthesis occurs Polyribosomal complex Allows for the synthesis of many protein molecules simultaneously from the same mRNA molecule
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