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