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What is a mutation? A mutation is a change in an organism's DNA. In the evolution section we discuss what these changes can do to an organism. Here we will talk about what these changes are and how they happen. We will cover four main types of mutation: Base change, insertion, deletion, and recombination.
What are Mutations
Base changes: These mutations occur when a DNA base switches from one nucleotide to a different nucleotide. A base change is a very small and often non-disruptive mutation.
Insertions: These mutations occur when a DNA base or bases get inserted into the genome. Insertions are often more disruptive than a base change mutation because they affect the downstream sequence. We will discuss why this can be so disruptive below. Deletions: Similar to insertions these mutations occur when a base or bases is removed from the genome. Deletions are also very disruptive for teh same reason insertions are disruptive, they often affect the downstream sequence.
Recombination: These mutations occur when a piece of DNA moves from one place in the genome to another, or can even come from outside the organism. Depending on how the recombination occurs this type of mutation has a lot of potential to give an organism new useful traits quickly.
What effects do mutations cause? The different mutations affect the organism differently. All four types of mutation can be neutral, deleterious, or beneficial (See the "Evolution" section for more on this). Here we will discuss in detail how each type of mutation affects the gene in which it occurs.
Base changes: As stated above these mutations are the least likely to be disruptive. A single base change does not affect the downstream sequence. Often a single base change will not change anything, except the base itself.
Insertions and Deletions: These two mutation types are often lumped as one because they affect the genome in a similar way. If you remember from the "components" section where we describe what the genome is made of we talked about the three-letter words or "codons". Imagine we add or remove a letter to one of these words. We have to shift all of the following letters down or up so that all the codons are still three letters. This changes all of the codons downstream of the mutation!
About the site: I developed as a companion website to Everything a cell does is a direct result of the genetics of that cell, whether it is a single-cell organism or part of a much larger organism. Thus, understanding the cells requires an understanding of the basis of all of their behaviors. About the author: I am a microbiologist studying microbial pathogenesis and the host immune response. My studies have included work in many pathogens including Rabies and Influenza viruses, Mycobacterium tuberculosis, Francisella tularensis, and Salmonella enterica. I currently live just outside of Philadelphia, PA, where I work as a postdoctoral fellow researching antigen processing and presentation during rabies infection. My email is always open for suggestions, corrections, or any other comments. Please feel free to contact me: