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Chapter 5new - Chapter 5 The Genetics of Bacteria and Their...

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Chapter 5 The Genetics of Bacteria and Their Viruses Suggested problems: #1, 3, 4, 6, 9, 10, 13, 19, 22, 26
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Why study bacteria? bacteria are prokaryotes , with very different genetics than eukaryotes they have been immensely important in the study of genetics understanding of the normal genetics of bacteria helps us understand the origins of some basic methods used in molecular biology
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Working with microorganisms unicellular has a single circular chromosome, not bounded by a nucleus they grow fast they can be grown in liquid or on a solid surface (agar plate) when spread on a plate, one bacteria will grow into a colony ; all cells from same ancestor are called a clone bacteria are prototrophic (can grow on minimal media)—autotrophic mutants can be isolated they have several different ways in which they share genetic information, allowing recombination
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Outline: Bacteria can exchange DNA among themselves in three ways: A. Via conjugation, by transfer of the F (fertility) factor from another bacterium B. From free DNA in the environment, called transformation C. From bacteriophages (viruses), called transduction
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Bacterial Conjugation: sharing of DNA between two living cells 1946 Lederberg and Tatum discovered conjugation: Physical contact between cells is required (they don’t “leak substances” to each other)
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The fertility factor (F) allows bacterial conjugation The F factor is a plasmid, a small nonessential circular DNA F has genes that allow the formation of pili , projections that allow a bacterium to make contact with another bacterium transfer of genetic material is unidirectional; only F+ strains can donate (recipients are called F-)
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Mechanism of bacterial conjugation F plasmid transfers one DNA strand to the recipient cell in a process called rolling circle replication
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Chapter 5new - Chapter 5 The Genetics of Bacteria and Their...

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