Genetic screening for suppressor mutation in Caenorhabditis elegans odr-3 mutants
A suppressor mutation is a mutation that negates the effects of a different, separate mutation, facilitating a return to the wild-type phenotype. In this experiment, a suppressor mutation screen of a mutation of the odr-3 gene was conducted by observing the egg-laying behaviors of mutagenized Caenorhabditis elegans worms in different chemical stimulants, and comparing the results to the wild-type. A mutant with a successful suppressor mutation of an odr-3 mutation will have similar egg laying behaviors to that of the wild-type (N2). The gene, odr-3, encodes a G protein α subunit that plays an integral role in sensory and olfactory neurons. The role odr-3 plays is vital to olfactory sensation, osmoregulation, and mechanosensory function. In this experiment, two worm lines that each had an odr-3 mutation and a potential suppressor mutation were generated, isolated, and tested: odr-3-JC-17 and odr-3-JC-66. When serotonin was introduced, the odr-3-JC-17 mutant strain showed a similar response in egg laying compared to the wild type, N2. The average number of eggs laid in an hour for each of the N2, odr-3, odr-3-JC-17 and odr-3-JC-66 strains in serotonin solution were 0.18 0.33, 0.21, and 0.44 eggs/hour, respectively. In dopamine solution, odr-3-JC-17 demonstrated similar egg laying behavior to N2. In a dopamine solution, the N2, odr-3, odr-3-JC-17 and odr-3-JC-66 strains laid 1.04, 2.25, 1.29, and 0.40 eggs/hour, respectively. When placed in an imipramine solution, odr-3-JC-17 had a significantly higher value of eggs laid in an hour than the odr-3 mutant. In imipramine solution, the N2, odr-3, odr-3-JC-17, odr-3-JC-66 mutant strains laid 1.56, 1.53, 2.80, and 0.91 eggs/hour, respectively. These results indicate the presence of a suppressor mutation that is at least partially effective in the odr-3-JC-17 mutant strain.