MUTATION RATE. “Currently, the rate of mutation in humans is estimated to be anywhere from 70–150 mutations per generation. By this line of reasoning, we would estimate that, at most, only 1% of the nucleotides in the genome are essential for viability in a strict sequence-specific way.”
http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004351