Biology 1002B Lecture Notes - Lecture 14: Acetyl Group, Lac Repressor, Allolactose
24 Aug 2013
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Genes get transcribed by many polymerases and translated from multiple ribosomes. In order to determine the oldest ribosome, look for the direction of the rna polymerase and note that the free mrna ends are the 5" ends. Promoters are understood as signals composed of dna. The lactose operon of e. coli was discovered by two scientists when they observed how e. coli had the ability to get energy from lactose as result of the enzyme galactosidease. Galactosidease breaks apart lactose into glucose and galactose and can also form the potential product allolactose (a lactose isomer) in a separate reaction with lactose. Normally, the activity of galactosidease as an enzyme is low, but not zero. In normal wild type phenotypes, adding lactose linearly expresses galactosidease (the lac operon is inducible by the presence of lactose). In mutant phenotype (lac -), galactosidease follows constituent expression with or without the presence of lactose (the lac operon lacks its usual inducibility).
