Gene mutations can be caused by such things as radiation and chemicals.
When they occur in sex cells, the mutations can be passed on to offspring;
if they occur in other cells, they can be passed on to descendant cells
only. The experiences an organism has during its lifetime can affect its
offspring only if the genes in its own sex cells are changed by the experience.
| NSES Content Standard C
Life Science: The molecular basis of heredity Grades 9-12, page 185 Changes in DNA (mutations) occur spontaneously at low rates. Some of these changes make no difference to the organism, whereas others can change cells and organisms. Only mutations in germ cells can create the variation that changes an organism's offspring. |