bacterial genetics1 (chapter 7) the beginning of chapters 7 is largely a review of topics covered in...
TRANSCRIPT
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.
Bacterial Genetics 2
The Bacterial Chromosome
Basic structureDNA double helixno nucleosomes
Replication
Plasmids
DNA replication
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’
Bacterial Genetics 4
What are the causes of mutations?
“Spontaneous” vs Induced
“Mutagens”
Chemicals
UV light
Ionizing radiation
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?
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
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
Bacterial Genetics 8
Transformation
Griffith & Avery Studies
Gene sources
‘Competent’ cells
Transformation
Bacterial Genetics 9
Transduction
Transfer mediatedBy virus
In “Specialized transduction”Specific genes are passed
Transduction
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
Bacterial Genetics 11
Hfr mediated conjugation
‘High frequency of recombination’
Plasmid integration
Consequences
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