LECTURE1Adunn

LECTURE1Adunn - Lecture 1A: Bacterial genetics Readings Ch...

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Unformatted text preview: Lecture 1A: Bacterial genetics Readings Ch 5, pages 181-207; 209-213 Typical Prokaryotic cell- Prokaryotes include bacteria and blue-green algae-defning Feature is DNA not located in membrane-bounded nucleus- genomic DNA is circular- oFten contains extra small DNAs called plasmids- viruses that grow in bacteria are Typical Prokaryotic cell- Prokaryotes include bacteria and blue-green algae-defning Feature is DNA not located in membrane-bounded nucleus- genomic DNA is circular- oFten contains extra small DNAs called plasmids- viruses that grow in bacteria are called bacterophages, or phages Bacterial colonies, each derived from a single cell Figure 5-3 Distinguishing lac + and lac- by using a red dye Table 5-1 Bacterial genetics:- markers are drug sensitivities and metabolic requirements- E. coli can grow on minimal plates with only carbon and nitrogen sources, salts and minerals, and energy source.- Mutations produced by treating cells with chemical mutagens- wild type cells called prototrophic , meaning they can synthesize all required factors for growth on minimal media- mutant type cells called auxotrophic , meaning they cannot synthesize one or more of the required factors. Model Organism Escherichia coli Model Organism E. Coli In the 1940s, Josh Lederberg and Ed Tatum began studying the sex-like heredity of E. coli cells, called bacterial conjugation. E. Coli has a single chromosme of 4.6 million base pairs with about 4000 genes. Grows rapidly in laboratory at 37 o C in liquid media or on agar plates. Can store bacterial strains for years in cryopreservative solutions at -80 C. Lederberg and Tatum experiment: first demonstration of bacterial conjugation Figure 5-5b Occurs at frequency of 1/10 7 No recombinants are produced without cell contact Figure 5-6 Neither strain yields prototrophic colonies. Proves that auxotrophs produced by mixing cells no due to diffusion of a small molecule from one strain to the other. Cells must come into physical contact to produce prototrophs.prototrophs....
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LECTURE1Adunn - Lecture 1A: Bacterial genetics Readings Ch...

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