Roy: It's not an easy thing to meet your maker.
Tyrell: What can he do for you?
Roy: Can the maker repair what he makes.
Tyrell: Would you like to be modified?
Roy: I had in mind something a little more radical.
Tyrell: What... What seems to be the problem?
Tyrell: Death. Well, I'm afraid that's a little out of my jurisdiction, you...
Roy: I want more life, fucker.
Tyrell: The facts of life. To make an alteration in the evolvment of an organic life system is fatal. A coding sequence cannot be revised once it's been established.
Roy: Why not?
Tyrell: Because by the second day of incubation, any cells that have undergone reversion mutations give rise to revertant colonies like rats leaving a sinking ship. Then the ship sinks.
Roy: What about EMS recombination.
Tyrell: We've already tried it. Ethyl methane sulfanate as an alkalising agent and potent mutagen. It created a virus so lethal the subject was dead before he left the table.
Roy: Then a repressive protein that blocks the operating cells.
Tyrell: Wouldn't obstruct replication, but it does give rise to an error in replication so that the newly formed DNA strand carries the mutation and you've got a virus again. But, uh, this-- all of this is academic. You were made as well as we could make you.
Roy: But not to last.
Tyrell: The light that burns twice as bright burns half as long. And you have burned so very very brightly, Roy. Look at you. You're the prodigal son. You're quite a prize!
Roy: I've done questionable things.
Tyrell: Also extraordinary things. Revel in your time.
Roy: Nothing the god of bio-mechanics wouldn't let you in heaven for.