Adding to TheoOdo's dialogue idea:
Luke: How did my father die?
Obi-Wan: Your father, who was a pupil of mine until he turned to evil, helped the empire hunt down and destroy the Jedi Knights... He betrayed and murdered your father, from a certain point of view. He ceased to be Anakin Skywalker and became Darth Vader. Anakin was seduced by the Dark Side of the Force...
Luke: The Force?
Obi-Wan: Before I can explain about the Force, you need to know more about Midichlorians. Without the midi-chlorians, life could not exist, and we would have no knowledge of the Force. They continually speak to us, telling us the will of the Force. When you learn to quiet your mind, you'll hear them speaking to you.
.::Obi-wan takes Luke's blood sample::.