Actin branching

1. Actin branching

3. Mutant analysis ? ARP2/3 BRK

4. Genetics starts with observation Observe variability Use genetics to understand the cause of the variability.

5. Easy example, flower color

6. A Mutagenesis Wild type Mutagen Legend (chemical, radiation, T-DNA,…) M1 plants Harvested In pools Mutant phenotype Pool 1 Pool 2 Pool 3, etc. Pools of M2 seeds Wild-type phenotype

7. B Screening Screen M2 pools (1, 2, etc.) for mutant phenotypes Legend M2 seedlings Mutant mut-1 Propagate mutant from mut1/mut-1 or from its mut-1/+ heterozygous siblings Mutant phenotype Re-screening M3 seedlings Establish segregation ratio Wild-type phenotype

8. First make sure the types are heritable and true breeding (homozygous for flower color alleles) All uniform Red by red X

9. X Red is dominant to White

10. Complementation tests can be made between recessive alleles. A dominant allele cannot be used. Why?

11. Complementation test distinguishes if one gene or two affects color Scenario 1: The two mutations are in the same gene mut1 mut1 X White 1 White 2 aa aa X mut2 One gene aa mut2 The mutations fail to complement each other.

12. Complementation test distinguishes if one gene or two affects color Scenario 2: The two mutations are in different genes a B X White 1 White 2 a B aaBB AAbb X A b Two genes AaBb A b These mutations complement each other.

13. x C Allelism Tests “How many genes are involved?” M3 plant mut-2/mut-2 M3 plant mut-1/mut-1 Legend Case 1: Case 2: Mutant phenotype mut-1/+ mut-2/+ No allelism Two genes mut-1/mut-2 Allelism Single gene Wild-type phenotype

14. We can isolate mutants We can test the mutations for allelism by a complementation test Two homozygotes are crossed. The resulting offspring has both mutations. Either the mutations are allelic and do not complement, or they are mutations in two different genes and they do complement.