Maybe this will help:
1. Line breeding is something you DO. E.g. breeding son back to mother to try to bring out a particular trait. We sometimes say a trait has been "selectively bred", when referring to a trait like tangerine. Line bred means gecko incest, breeding sons or daughters back to parents, or brothers to sisters. For selectively bred traits, yes the characteristics are encoded on the genes, but it is not a sure thing- just like two attractive people will sometimes have an ugly child, and vice versa. You can guess what the child might look like, and it will probably have some characteristics of either parent, but there are no guarantees, you really don't know how it will look until it grows up. In geckos, selectively bred traits include colors like melanistic, tangerine, snow and high yellow, and hypomelanism, and carrot tail. So if you breed two hypos together, you will most likely get a hypo but there is a possibility that you won't get a hypo at all, and also the possibility you may get a super hypo.
2. When you say "genetic", I am guessing you might actually be referring to "recessive", meaning a recessive genetic trait. A recessive genetic trait is something like blue eyes, where if both parents have blue eyes you are guaranteed the kid will have blue eyes. Recessive genetic traits include the three genetic strains of albinism, blizzard, and patternless. If you breed two Blizzards together, you will ALWAYS get blizzards.
I think that was what you wanted to know, hope that helped.
-----
Sarah Stettler aka Starling
Sarah@stargecko.com
StarGecko.Com COMING SOON! Star Quality Leopard Geckos
Specializing in Hypotangerine Tremper Albinos