If there is anything close to being immortal, that would be the proton and the tiny bit of consciousness carried with it. Scientists have done some math and found that if man has freewill, then so too does the matter of which he is composed.
A little higher up, as you allude, then it's the DNA. That is our "reincarnation". Our sole purpose, as far as I can see, is so that DNA can replication. And it is entirely possible that DNA is conscious.
This is a concept never before visited by me yet fascinating all the same!