Lab Chapter 3 From Genotype to Phenotype Notes

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20 Apr 2012
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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
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