Model organism

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Drosophila melanogaster, one of the most famous subjects for experiments in genetics

A model organism is a non-human species that is studied over many years, building up a lot of knowledge about it.

The purpose is to understand fundamental biological phenomena. The hope is that discoveries made in the model will give insight into how other organisms work.[1]

In particular, model organisms are widely used to explore potential causes and treatments for human disease when experimenting on humans would be impossible or less ethical.

This strategy is made possible by the common descent of all living organisms, and the conservation of metabolic and developmental pathways and genes over the course of evolution.[2]

Models[change | change source]

Model organisms in genetics[change | change source]

Drosophila melanogaster[change | change source]

Drosophila melanogaster was one of the first animals used for genetics. Today it is one of the most widely used and genetically best-known of all eukaryotic organisms.

All organisms use common genetic systems; understanding transcription and replication in fruit flies helps to understand these processes in other eukaryotes, including humans.[3]

Studies of X-linked traits confirmed that genes are found on chromosomes. Studies of linked traits led to the first maps of genetic loci on chromosomes. The first maps of Drosophila chromosomes were done by Alfred Sturtevant.

Drosophila melanogaster is one of the most studied organisms in biological research, particularly in genetics and developmental biology. Its complete genome was sequenced and first published in 2000.[4]

Because great deal is known about its development from egg to larva to adult, it is a key model for developmental genetics, or evo-devo. The hox genes, or homeobox, which control development in metazoa, were worked out first of all in Drosophila.

Escherischia coli[change | change source]

In 1946, Joshua Lederberg and Edward Tatum first described the phenomenon known as bacterial conjugation using Escherichia coli as a model bacterium.[5]

E. coli was an integral part of the first experiments to understand phage genetics,[6] and early researchers, such as Seymour Benzer, used E. coli and phage T4 to understand the topography of gene structure.[7] Before Benzer's research, it was not known whether the gene was a linear structure, or if it had a branching pattern.

E. coli was one of the first organisms to have its genome sequenced; the complete genome of E. coli K12 was published by Science in 1997.[8]

The long-term evolution experiments using E. coli, begun by Richard Lenski in 1988, have allowed direct observation of major evolutionary shifts in the laboratory.[9]

Other model organisms[change | change source]

References[change | change source]

  1. Fields S, Johnston M (Mar 2005). "Cell biology. Whither model organism research?". Science 307 (5717): 1885–6. doi:10.1126/science.1108872. PMID 15790833. http://www.sciencemag.org/cgi/content/summary/307/5717/1885.
  2. Fox, Michael Allen (1986). The case for animal experimention: an evolutionary and ethical perspective. Berkeley and Los Angeles, California: University of California Press. ISBN 0-520-05501-2.
  3. Pierce, Benjamin A (2004). Genetics: a conceptual approach (2nd ed.). Freeman. ISBN 978-0716788812.
  4. Adams M.D. et al. (2000). "The genome sequence of Drosophila melanogaster". Science 287 (5461): 2185–95. doi:10.1126/science.287.5461.2185. PMID 10731132. http://www.sciencemag.org/cgi/content/abstract/287/5461/2185. Retrieved 2007-05-25.
  5. Lederberg, Joshua; E.L. Tatum (October 19 1946). "Gene recombination in E. coli" (PDF). Nature 158: 558. doi:10.1038/158558a0. http://profiles.nlm.nih.gov/BB/G/A/S/Z/_/bbgasz.pdf. Source: National Library of Medicine - The Joshua Lederberg Papers
  6. "The Phage Course - origins". Cold Spring Harbor Laboratory. 2006. http://www.cshl.edu/History/phagecourse.html. Retrieved 2007-12-03.
  7. Benzer, Seymour (March 1961). "On the topography of the genetic fine structure". PNAS 47 (3): 403–15. doi:10.1073/pnas.47.3.403. PMC 221592.
  8. Frederick R. Blattner et al. (September 5 1997). "The complete genome sequence of Escherichia coli K-12". Science 277 (5331): 1453–1462. doi:10.1126/science.277.5331.1453. PMC 9278503.
  9. Bacteria make major evolutionary shift in the lab New Scientist