Medelian Genetic Principle #1The traits of an organism are determined by its genes Mendelian Genetic Principle #2Each organism has two alleles that make up the genotype for a given trait Mendelian Genetic Principle #3In sexual reproduction, each parent contributes just one of their alleles to its offspring Mendelian Genetic Principle #4In each genotype there is a dominant allele. If it exists in an organism, the phenotype is determined by that allele