BIO220 Lab 3 From Genotype to Phenotype Notes
•Genotype, not phenotype transmitted directly from parents to offspring
•Cntinuous phenotypic traits: interaction between multiple genes and often the
environment,
•Quantitative/polygenic traits
•Phenotype relies on interaction between environment and genotype
Caenorhabditis elegans
•Foraging behavior
•Consumes bacteria: nonharmful strain of E.coli (OP50)
•Discern edible bacteria from pathogenic bacteria, and quality of bacteria
•Behaviors: aerotaxis (movement toward/away from oxygen), aggregation,
locomotion
•Aggregate in clumps “social”
•Disperse evenly across lawn “solitary”
•Social versus solitary: single amino acid change at position 215 in NPR-1 gene
•Wilf social: Phe at position 215
•Solitary starins Val
•Null mutatnts of NPR-1 extremely social
•Both NPR-1 215F and NPR-1 215V suppress social feeding, NPR-1 215V does so
more strongly
•NoNPR-1 gene = very social, NPR-1 215F = social, NPR-1V = solitary
Notes from “The natural history of Caenorhabditis elegans”
•OP50 E.Coli mutant strain
•1-2mm as adult
•Human-made compost source of C.elegans
•In rotting plant material
•20°C, 3.5 to 4 days embryonic developmental period, and 4 juvenile stages L1 to
L4
•developmental arrest: diapause: reduced metabolism, increased stress resistance
•dauer alternative L3 stage: resistant to stressors and can survive without food for
several months whilst adults usually live 2 weeks
•L4 starved: develop into hermaphrodites that enter reproductive diapause
•L1 stage only stage that survives freezing
•Dauer entry induced by syngergistic effects of low food concentration, pheromone
sensation at high population densities, and high temperature
•Exit from dauer is irreversible. High food concentration and low temperature favors
dauer exit