The purpose of this research project is to develop and study mathematical models for certain biological phenomena at the molecular level. Current work has focused on (a) developing new estimates of the rate of recombination in finite Mendelian populations and studying the statistical properties of existing estimates, (b) analyzing the statistical properties of a general stratified sampling scheme for studying genetic variation in natural populations, (c) studying certain selective models which describe the evolution of a family of transposable elements and (d) applying existing methods in computational chemistry to help explain toxicological outcomes of environmental chemicals.