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Biology (196)
BIO-0013 (103)
Mc Vey (25)
Lecture

11-20-12.docx

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Department
Biology
Course
BIO-0013
Professor
Mc Vey
Semester
Fall

Description
11­20­12 • o this is a prokaryote because transcription and translation are occurring  simultaneously o the N terminus of a protein is made first • Puromycin o Antibiotic that inhibits bacterial transformation • Why study gene control in bacteria? o Roles bacteria play in our lives:  Medicine: disease­causing bacteria, health promoting bacteria  Biotech/industry: commercial value to manufacture products  (growth hormones, foods), degrade pollutants (oil, plastics),  research  Environment: making soil, controlling insects, snow formation • Bacteria are some of the most successful and abundant organisms on earth o Why: fast and easy replication, high mutation rate, able to adapt, simple  genome • Control of gene expression in bacteria o DNA▯RNA▯Protein▯post­TL o Ex: lactose metabolism  Positive and negative control o Many levels of control  Transcriptional control • Most energy efficient place to control  Translational control • Stop making protein  Post­translational control • Protein activation or inhibition • Chemical modification • Fastest way of control • Model system o Escherichia Coli o Uses a wide variety of foods for ATP production via glycolysis and the  ETC o Does not have a membrane bound nucleus  Circular chromosome  4000+ genes o uses glucose if available, but can metabolize other sugars if glucose is  absent  why do E.Coli prefer glucose to lactose? • Milk sugar is a disaccharide • Lactose  ▯Glucose + galactose o = catabolism • Galactose has to be modified before glycolysis can take  place  For e.coli to use lactose • Sugar must be able to get into the organism o Membrane protein – galactoside permease o Then bacterial cells break down (catabolism) the  disaccharide sugar into monosaccharides  Use enzyme β ­galactosidase (β ­gal)  Breaks β 1­4 linkage o Cells must have a way to know when they have  broken down enough lactose (when to stop)  Glucose indirectly causes the reaction to  stop  Catabolite repression of lac operon  When we have enough glucose, stop the  breakdown of lactose • How does bacteria use lactose as a food source? How do we know? o Jacques Monod and Francois Jacob o Finding mutations (cells that cannot metabolize lactose) o Replica plating
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