文档介绍：Chapte8 Microbial ics
DNA as ic material
Mutation
DNA repair
Microbial molecular biology and ics
A clone: a population of cells that are derived asexually from a parental cell and are ically identical.
Genome: all the genes present in a cell or virus.
Central dogma: DNARNA protein
transcription
translation
DNA as ic material
The Hershey-Chase experiments
RNA as ic material
TMV
Mutations and Mutants
Mutations: initially characterized as altered phenotypes or phenotypic expression, a mutation is a stable, heritable change in the nucleotide sequence of DNA.
Phenotype: the observable characteristics of anism
designated by a capital letter followed by two small letters, with either a plus and minus superscript to indicate the presence or absence of that property: His-, Glu+ et al.
Genotype: The precise ic make-up of anism
designated by three lower case letters followed by a capital letter (all in italics) indicating the particular gene involved: hisC, mutations in the hisC gene would be designated as hisC1, hisC2 et al.
Types of mutations
Conditional mutations: those that are expressed only under certain environmental conditions.
eg. : a conditional lethal mutant, low temperature grow; high temperature die.
Biochemical mutations: those causing a change in the biochemistry of the cell. Mutations make a anism unable to grow on a medium lacking an adequate supply of the pathway’s end product.
auxotrophs: the mutant cannot grow on minimal medium (MM) and requires nutrinent supplements.
prototrophs: microbial strains that can grow on MM.
Resistant mutant: a particular type of biochemical mutant that acquires resistance to some pathogen, chemical, or antibiotic.
Mutations occur in one of two ways:
1. Spontaneous mutations: arise occasionally in all cells and develop in the absence of any added agent.
2. Induced mutations: the result of exposure of anism to some physical or chemical agent called a mutagen.
Spontaneous mutations wi