Genetics: From Genes to Genomes

RNA polymerase is the key enzymefor transcription.• RNA polymerase involved in three phases oftranscription• Initiation – sigma subunit + core enzyme (two alpha, one beta,and one beta’ subunit)• Binds to promoter, unwinds DNA, begins polymerization of basescomplementary to DNA template• Elongation – movement away from promoter sigma subunitreleased, polymerization• Termination –signal reached by RNA polymerase• Rho dependent termination – Rho factor recognizes sequence in mRNA,binds to it, and pulls it away from RNA polymerase• Rho independent termination – stem loop structure formed by sequenceof 20 bases with a run of 6 or more U’s U s signals release of RNApolymeraseCopyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display17-5