The problems surrounding genetic tampering are that the smallest alteration changes us a great deal. After all, Chimpanzees and humans share over 98% genetics, yet look how very different we are. Just tweaking a single chromosome would cause unexpected results, and it really is like trying to paint a Da Vinci in the dark, upside down and with an audience demanding your attention. And don't forget the bats.
Humans, however, are mutating all the time. It's how our species has evolved over the millions of years to adapt to the planet we live in. If you were to alter the atmosphere by the slightest amount, we would be adversely affected in some rather nasty ways.
If you were to make out you are doing genetic tampering, you would need to first explain how you've studied many millions of mutations caused by said tampering, and how you counteract the negative affects that would come about by this.
Suddenly remembering a bulletin I once read about Chickens having teeth, from what I can remember our genetic structure is just a massive library of mutations that have certain elements switched on and others all set to dormant. If you knew which genetic markers to "switch on" you would be able to give humans any number of mutations, but it would be more like pinching designs off other creatures on our planet. So if you wanted wings say, you'd probably end up looking more and more like a vulture/bat human mutant.
Anyway, this is the chicken thing I mentioned, for those curious.
CHICKEN GROWS TEETH!?