What is the smallest self-replicating DNA sequence?

Mycoplasma pneumoniae has one of the smallest genomes known, with 816 kilobase pairs (kbs), so this will have the smallest natural self-replicating DNA sequence.

It all has to do with mutation. A mutation is a benefit, neutral or a detriment to SURVIVAL. A benefit or neutral tends to procreate and be carried into the next generation. A detrimental mutation tends not to and dies out, a dead end. So, one cell, became two cells acting as a community for a mutual benefit, then three cells, then four, and so forth. Millions of generations later, cells start to mutate and drift off into different functionality, and again, the beneficial and neutral survive to live another day. Somewhere in there, the single sexless cell, turned into a sexual pair, and THAT is where we went from snails who procreate asexually into sexual pairs. What you fail to see is that we have NO evidence or record of all the detrimental mutations that died out. And THAT is why evolution is still a theory. We can't prove it really IS happening as we THINK it is. We simply do not live long enough to see the results of the experiment we call life. Science works on experiments and observation and analyzing the RESULTS. Without results, we can only speculate and make an educated guess. Evolution is like a tree branching, with one species diverging from another through the different branches from a common ancestor that was close to but neither. The egg came first. It HAD to. A near-chicken laid an egg which was mutated by cosmic rays and became the chicken we know and love as Kentucky Fried. The parents were NOT chickens, but ALMOST chickens. WE are the survivors, of the process of mutations of either a beneficial or neutral effect in a chain back to the beginning of time. How may dead ends died out along the way? We are the sum total of ALL the mutations that have gone before... As for extinct creatures, it depends. Where would the DNA come from? The scenario of a mosquito trapped in amber in the movie Jurassic Park, actually IS feasible in theory, but no DNA has been found in practice. So, if we could get viable DNA, we COULD use cloning to inject that DNA into a cell and literally grow a clone of whatever DNA was found. Technically possible, but hardly likely in the near future...