Scott Baird (Committee Chair), Jeffrey Peters (Committee Member), Labib Rouhana (Committee Member)
Master of Science (MS)
In the cross of C. nigoni males to C. briggsae hermaphrodites, all F1 males arrest during embryogenesis. However in the reciprocal cross there are some viable F1 male progeny. This unidirectional male-specific lethality in the F1 hybrids has been attributed to a hybrid lethal gene in a 500 Kb region of the X chromosome of C. briggsae. Cbr-him-8 is a recessive maternal suppressor of the male-specific lethal phenotype, due to the requirement of the him-8 protein for proper X chromosome pairing. Without proper pairing of any one of the chromosomes in the Caenorhabditis genome, genes present on the unpaired chromosome will be silenced due to a process known as meiotic silencing of unpaired chromosomes (MSUC). It has been proposed that MSUC-based silencing of the X-linked hybrid lethal gene is the mechanism by which the male-specific lethality is suppressed. Based on this model, a co-suppression assay was used to identify the hybrid lethal gene. Transgenic strains of C. briggsae were constructed via microinjection of bacterial artificial chromosomes (BACs) of small portions of the X chromosome in which the hybrid lethal gene resides. The BACs were mixed with pCFJ909, a plasmid containing a functional cbr-unc-119 gene, this mixture was then microinjected directly into the gonad of cbr-unc-119 mutant hermaphrodites. A proportion of the resulting progeny incorporated the injected DNA into their nucleus and formed heritable extra-chromosomal arrays. These offspring were then selected based on the rescue of the unc-119 phenotype. Transgenic hermaphrodites were then mated to C. nigoni males and scored for viable F1 male progeny. Two BAC rescued the male specific hybrid lethal phenotype. Multiple other BACs failed to rescue the lethality phenotype. Focusing on a single BAC clone, using gene groupings and pCFJ909 the number of possible genes have been narrowed to two candidate hybrid lethal genes within the BAC 08G05. As well as 5 candidate hybrid lethal genes in the non-adjacent BAC 17D03.
Department or Program
Department of Biological Sciences
Year Degree Awarded
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