1.   And to this day, nobody knows how the disease first arrived in England, though it is possible that it simply arose there from natural genetic mutations.

2.   Another source of natural mutation comes from chemicals called free radicals our cells produce as part of their energy cycle.

3.   But sometimes differences arise as a result of natural mutation and uncontrolled cross-pollination in the wild.

4.   But natural mutations would have produced some semi-tough stalks that held the seeds more firmly in place.

5.   Junk DNA has a far higher natural mutation rate than functional DNA, which makes changes in the rate easier to detect.

6.   Since women are reaching menstruation at an earlier age, they are experiencing more menstrual cycles, more cell growth, and more natural mutation.

7.   That triggers the remaining cells to reproduce and the rate of natural mutation goes up.

8.   The grapefruit in question, the Rio Red, is the offspring of nature and science, of natural mutation and painstaking work in the lab.

9.   The natural mutation rate in such genes is so low that measuring a radiation-induced change is impossible.

10.   The strain could also have been produced in an academic or commercial laboratory for research or be a natural mutation never seen.