Lecture_1_(bacterial_genetics)

Lecture_1_(bacterial_genetics) - Lecture 1: Bacterial...

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Lecture 1: Bacterial Genetics (or “Everthing You Wanted to Know about Bacterial Sex but were Afraid to Ask”
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Bacteria Single celled, prokaryotic organisms. Infected with viruses that are called bacteriophage. Can transfer DNA from one cell to another - always unidirectional and partial . Can be grown on plates until a visible colony is formed - Cells all genetically identical = clone Often used common intestinal bacterium called Escherichia coli
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Growth of Bacteria
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Escherichia coli   Abundant, lives in your  gut   4000 genes   Circular genome is 4.6  million base pairs   Haploid Divides mitotically, in  an asexual mode There are ways that bacteria exchange genetic information, but they don’t  follow the same rules as eukaryotes.
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Bacterial Phenotypes - Most often based on ability to grow on a particular media 1) Prototrophs and auxotrophs. An auxotroph lacks the ability to grow on a particular nutrient. Example: A mutant strain that has lost the ability to synthesize its own supply of tryptophan is a Trp auxotroph and is designated Trp - 2) Ability to utilize substrates . The ability to utilize a particular carbon and energy source can also be used as a phenotype. Example: A strain harboring a mutation rendering it unable to utilize the sugar galactose is galactose-, or Gal-. 3) Antibiotic resistance . The ability to grow in the presence of an antibiotic. 4) Other markers include colony morphology and resistance to phage.
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Bacterial Phenotypes Lac+ (red) Lac- (white)
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A tryptophan auxotroph might have a loss-of-function mutation in any of five different enzymes that are involved in the biosynthesis of tryptophan. All are Trp- (phenotype), but each genotype is different
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Lecture_1_(bacterial_genetics) - Lecture 1: Bacterial...

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