Okay, in H'el on Earth storyark we learned that Superboy has 3 DNA line. Later I at least got impression that those DNA lines were Superman's, Lois and Jon's. If you read Secret Origins #7 you know that it isn't true.
- 45% Kryptonian (Superman, Jon)
- 45% Human (Lois, Jon)
- 10% Something else.
When they tested his blood in Star Labs the machine identified the species, not the actual donors. So, that 10% part isn't Lex's. I also would say that Star Labs have quite good parable system, so what the heck?