Rania Haddad

ranoosh427mail.fresnostate.edu

An understanding of how the natural selection of alleles is affected by the adaptation to the environment remains rudimentary for most species, including the nematode Caenorhabditis briggsae. Recent development of genomic resources and technological tools have advanced the utility of the genus Caenorhabditis as a model for studying genetic inheritance patterns. Further, recent efforts have enhanced our knowledge about the ecology of these nematodes. Thus, studying this genus should provide insight about the genetic basis of ecological adaptation. My goal is to study DNA inheritance patterns in hybrid lines created by crossing two genetically distinct strains of C. briggsae (AF16 and HK104) that were isolated from tropical and temperate habitats, respectively. Previous work has suggested that, when such hybrids are propagated at cooler temperatures (20 C), alleles of the AF16 strain are less prevalent in hybrids. This pattern suggests the possibility that population-specific alleles have helped wild populations adapt to their local temperatures. To test the hypothesis that temperature affects the retention of specific parental alleles in hybrids, I created a total of 90 AF16-HK104 hybrid lines at each of two temperatures (20 C and 25 C). I purified DNA and determined the DNA inheritance pattern for each hybrid line using Polymerase Chain Reaction (PCR) and gel electrophoresis genotyping followed by statistical analysis to identify significant deviations in the inheritance patterns of DNA. The results show that HK104 and AF16 alleles are incompatible at 20 C and there is an environmental-dependent epistasis on chromosome X. These findings will then motivate further studies to facilitate the understanding of how genetic variation helps organisms adapt to the surrounding environment.