Selection acts on the phenotype, but it is the genotype, not the phenotype,
which is inherited. Consider whether the genotype is less or more sensitive to selection if the allele in question 1) is dominant or recessive, 2) is distinguished from other alleles at the same locus by a synonymous or a non-synonymous point mutation, 3) contributes to one (ie. is non-pleiotropic) or multiple (ie. is pleiotropic) traits, and 4) contributes to a trait that is monogenic or polygenic. Using these four axes of allelic difference, describe what kind of allele would be most easily targeted by selection, and what kind of allele would be least easily targeted by selection. What would be the phenotypic effect over many generations of sustained very high selection pressure on an allele not easily targeted by selection, compared to one very easily targeted by selection?