[roflmyeggo]

There is a simple counter-example that proves that this is the wrong question to ask.

You cannot simply make a zygote with just the DNA from a sperm and an egg together alone. Both parents pronuclei are required for epigenetic reasons. If you try to do this, and the pronuclei are not present, then you will not make any viable offspring.

This is just one example of how oversimplified the model taught by the book is, though it is a useful one. The only thing that is certain is that we are not anywhere near being able to claim to know how many genes it takes to make a person.