The Basics of Mutations

By A.K. Matai

Mutations refer to the changes in the genetic sequence that can lead to changes at the RNA and protein level. These changes can have a wide variety of consequences. In this post, I will summarize the major types of mutations critical to the field of genetics.

Insertion & Deletion

Mutations Figure 1.jpg

Figure 1. Insertion of 2 or 3 Base Pairs. It is important to note that deletions follow a similar pattern as insertions. [A] The original DNA sequence. [B] Insertion of 3 base pairs (CTC) in the DNA sequence that results in the addition of Leu at the protein level. [C] Insertion of 2 base pairs (GC) in the DNA sequence that results in a premature STOP codon.

Insertions as well as deletions of base pairs have affects at the protein level. Insertion or deletion of 3 base pairs can result in the addition or deletion of an amino acid. Insertion or deletion of 2 base pairs usually result in a frameshift or a premature stop codon.

Substitution 

Substitutions can be spontaneous or induced which are outlined in Figure 2.

The Basics of Mutations 1.png

Figure 2. Spontaneous and Induced Mutations. [A] Spontaneous mutations can be transitions or transversion. [B] Mutations can be induced by mutagens. For example, 5 bromouracil (5BU) is a mutation that can pair with adenine as well as guanine leading to an AT to GC transition. [C] Point mutations can be silent, nonsense and missense. Silent mutations result in not change at the protein level. A nonsense mutation occurs when a point mutation results in a STOP codon. Missense mutations can be either conservative (a change to a similar amino acid) or non-conservative (a change to a vastly different amino acid). A conservative missense mutation can result in a protein that has partial function but a non-conservative missense mutation is more likely to cause major changes to the function or the protein.

Questions, Comments or Concerns?

Feel free to post a your questions, comments or concerns down below!

References

Locke, John; Deyholos, Michael; Harrington, Michael; Canham, Lindsay; Kang, Min, “Open Genetics Lectures (OGL) Fall 2016”

Unknown. DNA sequence. 2011. https://commons.wikimedia.org/wiki/File:DNA_sequence.jpg. Web. 19 Mar. 2017.

 

 

 

 

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