Yes, but when we are talking about "programming brain" we are assuming that changing few base pairs would change the behavior / structure. Ova don't grow

Yes, but when we are talking about "programming brain" we are assuming that changing few base pairs would change the behavior / structure. Ova don't grow into random jumbles of cells, most of the time they grow into babies. Exactly but can we change few base pairs and observe its effect? When we talk about reprogramming, we trying to figure out the cause and effect relationship, if a system is chaotic it is very difficult to figure out that relationship. Three bodies don't mutate into 4 bodies or weather does not changes into an ice age in an instant, but at the same time we cannot reprogram weather by introducing small changes.