An epigeneticist studies the influence of the environment on gene expression. So, things like long-term exposure to sun light or family dynamics would be good things to look for in her project.
It is the third one because the quiet rattle snakes are better adapted to their environment than the ones that rattle. So the ones that rattle ,which aren’t adapted to their environment, die off.
So cells have what are called telomeres. These act as a dividing limit. The point of limiting the amount of times a cell can divide and reproduce is to help prevent cancer. Cancer is simply uncontrolled division of unhealthy cells. By limiting cell division one can help prevent cancer.