Scott Baird (Advisor), Barbara Hull (Committee Member), Dan Krane (Committee Member)
Master of Science (MS)
Ray pattern is the most divergent morphological character among rhabditid nematodes. The ancestral ray pattern of Elegans group nematodes is commonly referred to as a 2(1)3+3 pattern, with rays 1 and 2 located anterior of the cloaca, ray 3 positioned at the cloaca, and rays 4-6 and 7-9 grouped in two clusters posterior of the cloaca. C. elegans males primarily exhibit the 2(1)3+3 pattern; however some isolates display variant patterns at a low frequency. The Hawaiian strain CB4856 exhibits a 3/3+3 pattern at a frequency of 0.09. In this pattern, ray 3 is located anterior of the cloaca in a cluster with rays 1 and 2. The designated wild-type strain, N2, is fixed for the 2(1)3+3 pattern. To examine the genetic basis of this phenotypic variation, recombinant inbred lines (RIL) derived from a ten-generation intercross between strains N2 and CB4856 were scored for ray pattern. Transgressive segregation was observed with the 3/3+3 ray pattern being expressed at much higher frequencies in many RIL than in either parental strain. QTL analyses of ray pattern data revealed a single highly significant QTL on the left side of chromosome V (LOD score = 14.273; p = 1.02e-10) as well as a marginally significant QTL on the right side of chromosome I (LOD score = 3.017; p = 0.109). To confirm the major QTL, CB4856 alleles from the left end of chromosome V were introgressed into an otherwise N2 background. From these data, a 500 Kb region of chromosome V was defined that has a major impact on the frequency of the 3/3+3 ray pattern.
Department or Program
Department of Biological Sciences
Year Degree Awarded
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