To find a gene, you have to associate a phenotype with a genotype (e. g. all individuals with white flowers have a certain allele). it is much harder to find genes that are involved in polygenic traits than it is to find the genes responsible for discrete traits. why? it's much more difficult to determine the dna sequence of alleles associated with polygenic traits. the alleles associated with polygenic traits are usually co-dominant. polygenic traits results from extensive gene by gene interactions, which makes finding individual genes difficult. it's harder to find one of the many genes involved in a polygenic trait vs. the only gene involved in a discrete trait..