Genome annotation

DNA annotation or genome annotation identifies genes and all of the coding regions in a genome and determines what those genes do. Once a genome is sequenced, it needs to be annotated to make sense of it. Gene annotation involves the process of taking the raw DNA sequence produced by the genome-sequencing projects and adding layers of analysis and interpretation necessary to extracting biologically significant information and placing such derived details into context.

Genome annotation consists of three main steps:

1. Identifying portions of the genome that do not code for proteins
2. Identifying elements on the genome, a process called gene prediction
3. Attaching biological information to these elements

Annotation can be subdivided as structural annotation, functional annotation, and comparative annotation (.i.e. both structural and functional) to leverage the understanding of this crucial topic.

Structural annotation consists of the identification of genomic elements.

1. Orfs and their localization
2. Gene structure
3. Coding regions
4. Location of regulatory motifs

Functional annotation consists of attaching biological information to genomic elements.

1. Biochemical function
2. Biological function
3. Involved regulation and interactions
4. Expression

DNA annotation reveals much of the information contained in the genomes; therefore, complete gene annotation is descriptive of organisms being and thus remains a milestone invention.

References:

1. Ejigu, G. F., & Jung, J. (2020). Review on the Computational Genome Annotation of Sequences Obtained by Next-Generation Sequencing. Biology, 9(9), 295.
2. Zhang, D., Guelfi, S., Garcia-Ruiz, S., Costa, B., Reynolds, R. H., D’Sa, K., … & Ryten, M. (2020). Incomplete annotation has a disproportionate impact on our understanding of Mendelian and complex neurogenetic disorders. Science advances, 6(24), eaay8299.
3. Koonin, E. V., & Galperin, M. Y. (2003). Genome annotation and analysis. In Sequence—Evolution—Function (pp. 193-226). Springer, Boston, MA.
4. Steward, C. A., Parker, A. P., Minassian, B. A., Sisodiya, S. M., Frankish, A., & Harrow, J. (2017). Genome annotation for clinical genomic diagnostics: strengths and weaknesses. Genome medicine, 9(1), 1-19.