Fig. 16-1 ter 12: Alternative approaches to mutational disse
Jan 02, 2016
Fig. 16-1
Chapter 12: Alternative approaches to mutational dissection
Types of mutational analysis
• 1. “Classical” “forward genetics” approach to understanding gene function: – Collect mutations. – Select those that affect the biological process of interest.– Study the mutant phenotype to discern the role of genes
in the process– Clone the gene and carry out molecular analysis
• 2. “Post-genomics” “reverse genetics” approach:– Start with the cloned/sequences gene of unknown function– Create mutants of the gene– Study the mutant phenotype to discern the biological role
of the gene
Selecting general mutagenic agents
Genetic screening versus selection
Genetic screen: produce and sort through many non-mutant individuals to find the rare desired mutation
Genetic selection: only the desired mutation survives
Fig. 16-4
Genetic screens can be carried out for a widevariety of biological functions (phenotypes):
• biochemical mutations• morphological mutations• lethal mutations• conditional mutations (restrictive/permissive conditions)• behavioral mutations
• secondary screens:
• modifier mutations• gene expression mutations (using “reporters”)
Fig. 16-6
Forward selection criteria: testing for auxotrophy
Fig. 16-7
Forward selection criteria: testing for phototaxis
Fig. 16-10
Forward selection criteria: cell cycle progression
Aspergillus nidulans
Fig. 16-12
Forward selection criteria: developmental morphology
Danio rerio
Fig. 16-13
Screen strategy: survey haploids for mutant phenotypes
Genetic screen strategies
• Haploid screen
• Diploid screen for dominant mutations (“F1 screen”)
• Diploid screen for recessive mutations (“F2 screen”)
• Diploid screen for recessive mutations – specific locus screen
• “Special tricks” screens
Fig. 16-14
Enhancer trap screen to identify tissue-specific enhancers
Reverse genetics
Knowing the sequence of a gene permits experiments to determine its function by directed mutation or phenocopy analysis
• Targeted gene knockout
Fig. 16-15
Knowing a gene sequence, it can becomea target for knockout or replacement
Reverse genetics
Knowing the sequence of a gene permits experiments to determine its function by directed mutation or phenocopy analysis
• Targeted gene knockout
• Site-directed mutagenesis
•
Fig. 16-16
Knowing a gene sequence, it can becomea target of in vitro mutagenesis
Fig. 16-16
Knowing a gene sequence, it can becomea target of in vitro mutagenesis
Reverse genetics
Knowing the sequence of a gene permits experiments to determine its function by directed mutation or phenocopy analysis
• Targeted gene knockout
• Site-directed mutagenesis
• Produce phenocopies with antisense RNA
Fig. 16-19
Knowing a gene sequence, it can becomea target for RNA-interference experiments
dsRNA induces cellular complexesthat degrade dsRNA
Fig. 16-18
Knowing a gene sequence, it can becomea target for RNA-interference experiments
Can induce RNA-specific degradation bydeliberately introducing dsRNA into cells
Look for phenotypes in RNAi-treated cells/organisms
Fig. 16-21
Fig. 16-22
Understanding the functional basis of dominant mutations
Fig. 16-22
Understanding the functional basis of dominant mutations
Fig. 16-22
Understanding the functional basis of dominant mutations
Fig. 16-22
Understanding the functional basis of dominant mutations
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Fig. 16-