Remember, genes are NOT blueprints. This means you can't, for example, insert the genes for an elephant's trunk into a giraffe and get a giraffe with a trunk. There are no genes for trunks. What you CAN do with genes is chemistry, since DNA codes for chemicals. For instance, we can in theory splice the native plants' talent for nitrogen fixation into a terran plant.
~Academician Prokhor Zakharov 'Nonlinear Genetics'