The DNA in the rod cells of your eyes contains all information needed to produce a complete baby. The DNA in an ear cell could theoretically construct a foot. We do not do these nonsensical things because in each of us large portion of the DNA template are blocked out. My DNA makes rod cells, nothing else. Each second, millions of cells die and millions of cells born, by the process of old cells pulling apart, each to make two new ones, exact duplicates. Fat cells, large storage bins, reproduce slowly but skin cells reproduce every 10 hours. One notable exception to this constant replacement is the brain. The moment you was born he had his lifetime maximum number of brain cells. Worn-out, damaged ones keep dying; they are never replaced. Yet your initial surplus was so great that you scarcely notices the loss.