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Bacterial Genetics 1 Bacterial Genetics (Chapter 7) The beginning of Chapters 7 is largely a review of topics covered in Biol 131, and our focus will be on the sections beginning with “Mutations to Genes” How is knowledge of bacterial mutation and recombination important? -- Evolution -- Antibiotic resistance -- Genetic engineering How do bacteria obtain new traits? Spontaneous mutation -- or experimentally ‘induced’ From other cells “Genetic recombination” We will discuss the basic steps used in genetic engineering, and you should read the pertinent sections of Chapter 8.
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Page 1: 8 Genetics

Bacterial Genetics 1

Bacterial Genetics(Chapter 7)The beginning of Chapters 7 is largely a review of topics covered in Biol 131, and our focus will be on the sections beginning with “Mutations to Genes”

How is knowledge of bacterial mutationand recombination important?

-- Evolution-- Antibiotic resistance-- Genetic engineering

How do bacteria obtain new traits?Spontaneous mutation

-- or experimentally ‘induced’

From other cells“Genetic recombination”

We will discuss the basic steps used in genetic engineering, and you should read the pertinent sections of Chapter 8.

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Bacterial Genetics 2

The Bacterial Chromosome

Basic structureDNA double helixno nucleosomes

Replication

Plasmids

DNA replication

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Bacterial Genetics 3

Genetic mutations are changes to the genetic code

Some common types and effects of mutations

chemical alterations

base substitution

deletions -- cause shift in

‘reading frame’

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Bacterial Genetics 4

What are the causes of mutations?

“Spontaneous” vs Induced

“Mutagens”

Chemicals

UV light

Ionizing radiation

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Bacterial Genetics 5

Mutations and evolution of bacteria

Do all mutations lead to beneficial changes?

Do mutations create beneficial changes in response to specific environment ‘stresses’ (such as high temperature)?

Will a beneficial mutation always spread through a population? -- under what conditions?

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Bacterial Genetics 6

The Ames test -- book doesn’t describe this well

Bioassay for chemical mutagenicity

Salmonella typhimurium used is a

His- ‘auxotroph’

“Positive selection” for a ‘back mutation’ to His+

(compare to negative selection in the book)

mutagens and carcinogens

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Bacterial Genetics 7

Bacterial Genetic Recombination

Processes by which bacterial genesare obtained from other organisms

= “Horizontal gene transfer”

Three processes:

1) Transformation

2) Conjugation

3) Transduction

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Bacterial Genetics 8

Transformation

Griffith & Avery Studies

Gene sources

‘Competent’ cells

Transformation

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Bacterial Genetics 9

Transduction

Transfer mediatedBy virus

In “Specialized transduction”Specific genes are passed

Transduction

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Bacterial Genetics 10

Conjugation

Genes carried on a F-plasmid

Process of conjugation

Loss of F+ phenotype

Plasmids can carry other genes

R-plasmids

Virulence plasmids

Other nonessential traits

Conjugation

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Bacterial Genetics 11

Hfr mediated conjugation

‘High frequency of recombination’

Plasmid integration

Consequences

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Bacterial Genetics 12

Use of Bacteria in Biotechnology

Role of plasmids

‘Cloning’ of useful genes

Bacterial ‘drug factories’

Bio-engineering of other organisms

Genetic Engineering