BIOL 102 Lecture Notes - Lecture 22: Trp Operon, Lac Operon, Lac Repressor
Document Summary
Prokaryotes and eukaryotes alter gene expression in response to changing environment. In multicellular organisms gene expression regulates development and is response for differences in cell types. Operon: entire stretch of dna that includes operator, promotes and genes they control. Ex: trp operon (active repressor), be default trp operon is on and tryptophan synthesis happens. Operon can be switched off by repressor: product of separate regulator gene and prevents transcription by clocking rna polymerase, can be active or inactive. Corepressor: molecule at cooperates with repressor protein to switch operon off. Repressible operon: usually on binding of repressor to operator to stop transcription. Inducible operon: usually off an inducer inactivates repressor and turns on transcription. Lac repressor is active and is an inducible operon. Inducible enzymes usually function in catabolic pathways: synthesis induced by chemical signal. Repressible enzymes usually function in anabolic pathways synthesis repressed by high levels of end product.
