You do however build software. Even with DNA, if you manually assemble a sequence, is it not something you've built? DNA imo is special not because of being something you discover, but because it's an integral part of everyone and the process by which sequences occur naturally is too random to guarantee that a sequence will remain unique.
Software on the other hand, is still the product of a thinking mind, so it should be given proper protections as intellectual property. However, the standard for the patent needs to be much higher than it is right now (presumably because those determining the uniqueness of the idea aren't all that experienced or up to date with the industry the idea relates to).
Either that or a better way for people to contest the validity of patents.
Yes. You don't invent or build math; you discover it. It's nature.
Patenting DNA is also silly for similar reasons.