BI226 Lecture Notes - Lecture 6: Stem-Loop, Operon, Escherichia Coli
Document Summary
E. coli has over 3,000 genes in its bacterial genome. How does it control which genes are turned on and which ones are turned off . This is the first level of control of gene expression at the transcriptional level. Rna polymerase participates in all three phases of transcription. Initiation core rna polymerase plus sigma ( ) factor. Elongation core rna polymerase without factor. Rho-dependent rho ( ) protein binds to rna polymerase and removes it from. Rho-independent 20 nt sequence in rna forms stem-loop (hair pin appears and bumps off the rna) Sequences for start and stop of transcription are distinct from sequences for the start and stop of translation mrna are often polycistronic (encode >1 protein) Regulation of expression can occur at many steps. Most critical step in regulation of most prokaryotic genes. Require repressible regulation pathway turned off unless the cell needs more of the larger molecule.