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Gene Mutation Basics: Causes and Types

Here's how gene mutations actually happen, and why they aren't always a bad thing.

  1. What is a mutation?

    A mutation is a permanent change in the DNA base sequence that differs from the original.

  2. What causes mutations

    Mutations can arise naturally from errors that occur while DNA is being copied, or they can be caused by external factors (mutagens) such as ultraviolet light, radiation, or certain chemicals.

  3. Types of mutations

    Mutations range widely β€” from a point mutation, where a single base is swapped for another, to insertions or deletions of bases, all the way up to large-scale mutations where part of a chromosome changes wholesale.

  4. Mutations aren't always harmful

    Most mutations are either harmful or have little to no effect and are neutral, but in rare cases a mutation produces a trait that's advantageous for survival β€” and such mutations can spread through a population via natural selection, becoming a driving force of evolution.

  5. Germline mutations vs. somatic mutations

    A mutation that occurs in a germ cell, like an egg or sperm, gets passed on to offspring, while a mutation in a somatic (body) cell only affects that individual and isn't passed down to the next generation.

  6. A well-known example

    Sickle cell anemia, caused by a single base change in the gene for hemoglobin, shows that even one single base change can produce a clear change in the shape and function of red blood cells.

There's no such thing as perfect copying

Every time a cell divides, its DNA is copied with remarkable accuracy, but errors occasionally slip in during that process, and DNA can also be damaged by external factors. Changes that appear in the base sequence this way are called mutations, and mutations also play an important role in a species' diversity and evolution.

See the technology for correcting mutations, too

Gene-editing technology that can precisely correct unwanted mutations β€” or, conversely, deliberately introduce a change at a specific location β€” has been advancing rapidly in recent years, using tools like CRISPR gene editing.

Frequently Asked Questions

Are mutations always bad?

No. Most mutations are either harmful or have almost no effect, but on rare occasions a mutation creates a trait that's advantageous for survival, and such mutations can spread through a population via natural selection, becoming a driving force behind evolution.

Why does a lot of UV exposure increase the risk of mutations?

Ultraviolet light can cause abnormal bonds to form between the bases that make up DNA, introducing errors into the base sequence β€” and if that damage isn't properly repaired, it can remain as a permanent mutation.