The fact is the genetic code of a creature only has that code for body parts, tissues, cells, organs, and systems of that particular creature.
Actually we find that's not true. Often the genetic code of a creature contains not just the information for the body parts that it
has, but for body parts, tissues, cells, organs, and systems that it
used to have, previously in its evolutionary history.
For instance, human beings can't manufacture Vitamin C. That's why we have to ingest it to survive. But we have the gene to do it, only it's in a deactivated state. Our evolutionary ancestors were able to synthesize that vitamin, and we inherited the gene, only it's got a stop codon somewhere in the middle, so it doesn't work.