Genetics, Disease and Dentistry

Educational Resource from NCHPEG

Genetics Primer - What are Mutations?

Article Index
Genetics Primer
What are genes?
Why do we have two copies of each gene?
What are Mutations?
What is AD inheritance?
What is AR inheritance?
What is XLR inheritance?
All Pages

What are mutations?

Changes in the DNA code (mutations) can be beneficial, neutral, or harmful. Genetic mutations can be inherited from the mother, from the father, from both, or they can appear for the very first time in an individual (new mutation). Whether a mutation is harmful depends on how the altered code in the DNA affects its instructional message:

Normal message: GET THE RED HAT.

Mutation 1: GET THE RED CAP.

Two letters have changed, but the end product is not significantly altered. This represents a neutral change that is not likely to disrupt the resultant protein and it's function.

Normal message: GET THE RED HAT.

Mutation 2: GET THE RED CAT.

Only one letter has changed, but the end product is significantly altered. This represents a harmful change in the resultant protein product of this gene, which may manifest in disease.

Four letters in the DNA code

There are only four letters in the DNA code: A, T, C, and G, short for adenine, thymine, cytosine, and guanine. Just like in the analogy with the red hat, one letter can be changed, deleted, or added. In addition, entire pieces of code (i.e., whole words and sentences) can be spelled backwards, cut and pasted where they don't belong, or cut short, all of which can change the form and function of the end protein product in the body.

Mutations and the environment

Keep in mind that the impact of a mutation also depends on the environment in which it is expressed. The same mutation can be harmful in one environment, neutral in another, and beneficial in still another. For example, a mutation in the gene that codes for one part of the hemoglobin molecule can cause considerable damage and discomfort at extremely high altitudes, but cause no problems at all at sea level. Other mutations may not become harmful to an individual unless he or she is exposed to a toxic chemical, carcinogen, allergen, or a specific environmental agent that acts on a genetic susceptibility. Beneficial mutations include those that have allowed our species to acquire new, adaptive structures and functions during evolutionary history (e.g. opposable thumbs, binocular vision). There would be no evolution in any species without the genetic variation produced, in part, by mutations.

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