BIOLOGY 172 Lecture Notes - Lecture 22: Beta-Galactosidase, Cellular Respiration, Genetic Screen
Document Summary
Lecture 22 - gene expression & information flow. Animal cells have dna for all cells in them. Translating all genes all the day is not efficient. Gene expression can be regulated at the level of: Constrictive expression - gene product made continuously. Genes needed all of the time (ie. genes for enzymes in glycolysis) Regulated expression - gene product made on demand; expression can be induced or repressed (turned on or off) E. coli use many sugars for metabolism. Glucose is the preferred source of carbon -- used directly in cellular respiration. If not glucose is available, bacteria can break down lactose to generate glucose. Beta -galactosidase: lactose -> galactose & glucose. Finding genes for lactose metabolism in e. coli. Genetic screen - find a mutant that has a defect in the gene necessary for lactose metabolism. 100,000 e. coli -> mutagen -> each cell has a different mutation.
