The genetic code does not, and cannot, specify the nature and position of every capillary in the body or every neuron in the brain. What it can do is describe the underlying fractal pattern which creates them.
Nonlinear Genetics
Gene Splicing
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.
Nonlinear Genetics
Centauri Genetics
It is a medical commonplace that the tissues of the human body replace themselves regularly, essentially creating an entirely new body every seven years. From whence then come cancer and the slow degeneration of age? They exist as faults in the patterns of intelligence within the genes themselves; by reprogramming these smallest parts, the whole becomes well.
Nonlinear Genetics
Nanohospital