Mutational Effects on Quantitative Traits of Arabidopsis thaliana

9629457 Shaw Spontaneous mutation is the ultimate source of genetic variation which is the basis for evolutionary divergence due to selection and drift. Theory concerning the evolutionary consequences of spontaneous mutation in genes affecting quantitative traits of multicellular organisms has been well developed over the past 20 years. This work has revealed that inference of the evolutionary consequences of mutation depends on detailed information, including the rate of introduction of variation due to mutation, per genome mutation rates, the distribution of mutational effects, and gene action of mutant allele. Mutation rate derived from the occurrence of readily detectable effects ('visible mutations') have been documented for many traits. These, however, likely underestimate rates of evolutionarily significant mutation because they fail to account for mutations of small effect. Empirical studies, most focusing on Drosophila melanogaster, have provided evidence concerning aspects of mutations affecting quantitative traits, and for some of these aspects consensus is gradually emerging. The few available studies on other organisms have tended to be limited in scope. In particular, very little information is available from plants, though they offer a clear experimental advantage for studies of mutation in that seeds representing distinct generations can be stored for eventual simultaneous rearing in a common environment. The experiments proposed here are designed to estimate the properties of mutations affecting quantitative traits in the annual crucifer, Arabidopsis thaliana. This study will employ lines of A. thaliana that have previously been advanced from a single founder through 17 generations. The proposed experiments will assay variation among lines derived from a common founder and also among progenies resulting from formal genetic crosses among lines. The major goals of this study are: (1 ) to infer distributions of mutational affects, (2) to assess the mode of inheritance of newly arising mutations, and (3) to infer the parameters of gene action, including dominance, epistasis, and pleiotropy.