 Although genes contain all the information an organism uses to function , the environment plays an important role in determining the ultimate phenotypes an organism displays . This is the complementary relationship often referred to as " nature and nurture " . The phenotype of an organism depends on the interaction of genes and the environment . An interesting example is the coat coloration of the Siamese cat . In this case , the body temperature of the cat plays the role of the environment . The cat 's genes code for dark hair , thus the hair @-@ producing cells in the cat make cellular proteins resulting in dark hair . But these dark hair @-@ producing proteins are sensitive to temperature ( i.e. have a mutation causing temperature @-@ sensitivity ) and denature in higher @-@ temperature environments , failing to produce dark @-@ hair pigment in areas where the cat has a higher body temperature . In a low @-@ temperature environment , however , the protein 's structure is stable and produces dark @-@ hair pigment normally . The protein remains functional in areas of skin that are colder – such as its legs , ears , tail and face – so the cat has dark @-@ hair at its extremities . 
