Written by Bethany Stoutamire (Former SDSU Extension Aging in Place Coordinator AmeriCorps VISTA Member) 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, repairing, breaking down, and consuming energy. Like a car or computer, when our bodies are young 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 thus there is more likely to be a mistake when it’s fixed, creating a mutation. 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 telomeres 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 a telomere begins 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 that genetically identical mice can still have variations in lifespans due to epigenetic changes.
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. It is also important to note that 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.
Stay tuned for the next article in the Cultivating a Healthy Life Series when we discuss strategies shown to enhance our health and well-being at later stages of life.
Cultivating a Healthy Life Series:
- Cultivating a Healthy Life
- 5 Myths About Aging
- Why Aging Myths Matter
- We Are What We Think
- 5 Steps to Age Gracefully
- Moving Forward Together
- 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:
- Why Your DNA Isn't Your Destiny
- What is a Gene Mutation and How Do Mutations Occur?
- What is the Epigenome?
- National Institute on Aging. 2011. “Biology of aging: Research today for a healthier tomorrow.”