I had a thought recently; considering reproduction in animals (for simpicity, let me assume mammals) via a programming metaphor. The DNA contributed by mother and father is the source code; the mother's womb is the compiler; and the baby is the executable code.

The first thing that's noted is that there is a very good chance (around 50%) that the executable code will include its own compiler. And this immediately leads to the possibility that the compiler can slip in any little changes to the executable code that it wants; it can, in fact, elect to entirely ignore the father's input and simply clone itself. (It seems that it doesn't). Or, in other words, the DNA is quite possibly only a partial description of the resulting baby.