I suspect neither Gryphon nor Joe Martin ever bothered pinning down exactly how this works, but Omega-2 is a retrovirus to start with, so it's already got a mechanism for splicing itself into the human genome. I don't see why it couldn't ensure that two copies of itself were present in every cell of any fertilized embryo with at least one Detian parent.

(The real trick, to my mind, would be accomplishing this while still making it nigh-impossible to reverse engineer Omega-2 from a gene sample of an adult Detian, as has also been established is the case.)