The unique code of DNA you were born with (your personal genome) affects your health, appearance, and many other traits that make you unique. However, that is only part of the story. Your genome is dynamic over the course of your lifetime, and your environment plays a role in how your genes work. Consider the following:
There are trillions of bacteria, viruses, and yeast and other fungi (collectively called microbes) that live in and on your body. The DNA from all the microbes on your body is called your microbiome, and genes from these microbes outnumber your own roughly 300 to 1! The make-up of your microbiome can affect your health, your digestion, and maybe even your mood. Your microbiome is ever-changing, influenced by the foods you eat, the people you kiss, the surfaces you touch, your use of antibiotics and sanitizers, and more.
Mutations are simply changes in one’s DNA sequence and are not necessarily bad or good. Mutations can arise when a cell makes a mistake copying its DNA or upon exposure to environmental insults, such as UV rays or certain chemicals. When a mutation arises in a cell, the DNA in that cell is then slightly different from the DNA in the neighboring cell, and this is called mosaicism. When the cell divides, it will pass on the mutation to its descendants. (Note: only certain cells in our bodies can give rise to egg and sperm. Therefore, a mutation that arises in a cell in your big toe will not be passed down to your children.)
Some people carry genetically distinct cells that originate from another individual. This phenomenon, called chimerism, can arise in people who have received bone marrow transplants or women who have carried a pregnancy.
Your environment & epigenetics
In addition, personal genetics reflects the influences of our environment, lifestyle, and social experiences on how our genes work (epigenetics). There is even evidence suggesting that these influences can be passed down from one generation to the next (so-called transgenerational epigenetic inheritance).
As a result, our genes are only part of a much more complex story of who we are and what our future holds. The growing field of personal genetics is at the intersection of science and society; it is both an exploration into the complex interactions through which our genes and our environment influence our physical, mental and behavioral states as well as an on-going conversation on the meaning for individuals and society.