MICRB316 Lecture Notes - Lecture 7: Lac Operon, Leucine Zipper, Cyclic Adenosine Monophosphate
8 Mar 2014
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Document Summary
Control of gene expression is essential to life. Genes in prokaryotes regulated together transcriptionally are called operons. Co-regulation of genes used for a given situation. Genes must be regulated so that energy is used efficiently. Late 1950"s, the 1st example of a regulatory protein was discovered during a genetic study of the e. coli lac operon. Monod et al. noted mutants that showed constitutive expression of b -galactosidase rather than inducible, normal expression. Induction could be restored by introducing genetic material in trans. Postulated that the dna encoded a repressor (laci). This led to the notion that all regulation was due to repressors. Not until the late 1960"s did experiments with arabinose and maltose operons challenge this view. Now, hundreds of activators and repressors are known. Some are specific acting at a few loci (laci) Others are global regulators controlling 100"s of genes (fur) Sequence analysis shows that most activators an repressors belong to a small number of families .
