The Science of Aging Back »

Written by Bethany Stoutamire under the direction and review of Leacey E. Brown.

Note: Definitions for the italicized words can be found under Key Terms.


From the moment we are born, our cells are constantly dividing and repairing and breaking down and consuming energy. Like a car or computer, when our bodies are younger they usually run pretty smoothly. As time passes, cellular damage starts to accumulate, increasing our risk of developing disease or disability.

What causes cellular damage?

  • Genetic mutation
    There are approximately 25,000 genes made up of approximately 3 billion base pairs that comprise our DNA. A mutation can be caused by a mismatched base pair in the genetic code or a broken strand of DNA. The latter is much more difficult for the body to repair and there is more likely to be a mistake. Sometimes, these mutations can be passed down from parent to child, while other times they can be caused by environmental factors, such as exposure to UV radiation from the sun.
  • Cell Division
    Another type of cellular damage occurs when a cell divides and passes on its genetic information onto its two daughter cells. A telomere is a stretch of DNA at the ends of chromosomes that protect the DNA. Each time a cell divides, the telomere shorten. Once the telomere becomes too short, it can no longer protect the DNA. When this happens, cells are more likely to malfunction. While shorter telomeres are a normal part of the aging process, activities such as smoking, sitting too much, etc. can accelerate the cell division process, ultimately causing the telomere to become shorter more quickly than what would be considered normal aging. Cancer is an example of what happens when telomere begin to malfunction.

Emerging Field of Study

Epigenetic changes are chemical compounds that when attached to genes can change how the genes express themselves. The epigenome consists of all the chemical compounds that have been added to one’s DNA. Changes in the epigenome can result in changes in gene activity. The epigenome can be affected by lifestyle and environment (e.g., smoking). For instance, scientists have observed in genetically identical lab mice that there is still a variation in lifespan.

As John Cloud explains, “Epigenetic changes represent a biological response to an environmental stressor. That response can be inherited through many generations via epigenetic marks, but if you remove the environmental pressure, the epigenetic marks will eventually fade, and the DNA code will--over time--begin to revert to its original programming.”

Hope for the Future

While we still have a lot to learn about the mechanics of aging, evidence suggests that the changes described above do not mean disease after age 65 is to be expected. Lifestyle factors, such as not smoking, wearing sunscreen, attitudes and beliefs, diet and exercise play an import role in the disease process. In addition, like new cars or computers, cells sometimes cease to function properly early in life, resulting in disease. However, this does not mean preventing disease is a hopeless endeavor.

Cultivating a Healthy Life Series:

Key Terms

  • Cell - The structural biological unit of all organisms. It is bound by a membrane and contains various biomolecules.
  • Gene - A segment of DNA that is used as a blueprint to make proteins. They are responsible for many heritable traits.
  • Base Pairs - Complementary nucleic acid molecules. In DNA Adenine (A) binds with Thymine (T) and Cytosine (C) binds with Guanine (G).
  • DNA - Stands for deoxyribonucleic acid. DNA contains the genetic code for all living organisms from plants to bacteria to humans.
  • Chromosomes - A structure found in the nucleus of cells that carries genetic information in the form of genes.

References & Additional Readings:

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