4 Types of Genetic Alterations

Gene alterations associated with genetic diseases include a variety of mutational types including deletion, single nucleotide changes, duplication, and inversion1,2

COMPLEX-DISEASES

Duplication

  • Consists of a piece of DNA being copied once or many more times. This duplication could occur within the same gene or could result in duplication of a section of a chromosome (chromosomal duplication), resulting in multiple copies of genes within that chromosomal region3,4
  • Duplication within a gene can result in the function of the resulting protein being altered due to the change in the amino acid sequence1. Chromosomal duplications and the corresponding increase in copy number of particular genes can result in increased production of the corresponding proteins5

Inversion

  • An inversion occurs when two breaks occur in one chromosome and the region between the breaks flips 180 degrees before rejoining with the two end fragments, thereby resulting in the sequence being reversed6
  • Inversions can occur within a single gene or can occur across several genes in one chromosome6,7

Deletion

  • Involves the loss of a piece of DNA from the replication strand, resulting in a reduction in the number of DNA base pairs3
  • A deletion could occur within one gene, resulting in the loss of base pairs in that gene, or could result in deletion of a section of a chromosome, resulting in the removal of one or several neighbouring genes3
  • For a deletion within a single gene, the change in DNA sequence may result in altered function of the protein product due to changes in the resulting amino acid sequence3

Single Nucleotide Change

  • Involves a change in a DNA base pair in the gene3
  • This single nucleotide change causes a change in the amino acid encoded by the surrounding DNA sequence. This one small change can result in altered function of the resulting protein3,4

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  1. NIH. What kinds of gene mutations are possible? Available at: https://ghr.nlm.nih.gov/primer/mutationsanddisorders/possiblemutations. Accessed November 15, 2018.
  2. Griffiths AJF, et al. An Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000. Inversions. Available at: https://www.ncbi.nlm.nih.gov/books/NBK22042/. Accessed January 2, 2019.
  3. NIH. What kinds of gene mutations are possible? Available at: https://ghr.nlm.nih.gov/primer/mutationsanddisorders/possiblemutations. Accessed January 29, 2019.
  4. Nature Education. A single base change can create a devastating genetic disorder or a beneficial adaptation, or it might have no effect. How do mutations happen, and how do they influence the future of a species? Available at: https://www.nature.com/scitable/topicpage/genetic-mutation-441. Accessed January 29, 2019.
  5. Nature Education. A single base change can create a devastating genetic disorder or a beneficial adaptation, or it might have no effect. How do mutations happen, and how do they influence the future of a species? Available at: https://www.nature.com/scitable/topicpage/genetic-mutation-441. Accessed January 29, 2019.
  6. Griffiths AJF, Miller JH, Suzuki DT, et al. An Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000. Inversions. Available at: https://www.ncbi.nlm.nih.gov/books/NBK22042/. Accessed January 2, 2019.
  7. Bowen DJ. Mol Pathol 2002;55(2):127–144.