text: There is not a single human trait that is not affected by the environment.  DNA contains codes for proteins, which differentially affect cell metabolism.  The genes themselves are dependent on their environment (ie., the cytoplasm of the cell that surrounds them).  Depending on the composition of the cytoplasm, genes are expressed differently, and this is one major source of cell differentiation during mitosis in a zygote.  The bottom line is this: Even traits that seem to be directly linked to genes can be influenced by environment.  Take, for instance, the genetic disorder phenylketonuria.  In this disorder, the body lacks the enzyme necessary to convery phenylalanine to tyrosine.  Levels of phenylalanine reach toxic levels, causing irreversible mental retardation.  We now know that if this is diagnosed early that hte mental retardation can be completely prevented by diet.  Also, think about the effects of teratogens (environmental agents with the potential to cause birth defects).  Environmental toxins during pregnancy can affect the developing fetus and alter any aspect of its physical or mental development.  The bottom line: phenotypic expression is not the same as genotype.  EVERY trait has the potential to be influenced by the environment.