I don't understand how you see this process as a genetic algorithm... There is no combination of genetic traits between subroutines to make new ones, no killing of unfit subroutines and you don't even try to explain how random mutations come into being and how the fastest subroutine is also evaluated as the best one to do a particular thing.
Before trying to fit a square into a round hole, please just read up on neural networks and backpropegation which more closely resembles your own description on how the brain works.
I don't understand where yo get your 400 billion from, even if it's possible, observations I googled (I don't have the time to spend a workweek understanding precisely what scientist agree on) all come down to 20-1000 switches per second average across the brain (link your article if you don't agree). That's not even near 400 billion. More importantly a transistor can't hold even remotely the amount of information to represent a neuron. You would need at least a transistor for the neuron itself and one for every connection it has (average of a 1000) to other neurons, which is still wildly inaccurate. Your estimate needs some serious adjustment.