Editing Model organism (section)

== Use ==
There are many model organisms. One of the first model systems for [[molecular biology]] was the bacterium ''[[Escherichia coli]]'', a common constituent of the human digestive system. Several of the bacterial viruses ([[bacteriophage]]) that infect ''[[Escherichia coli|E. coli]]'' also have been very useful for the study of gene structure and [[gene regulation]] (e.g. phages [[Lambda phage|Lambda]] and [[Enterobacteria phage T4|T4]]). However, it is debated whether bacteriophages should be classified as organisms, because they lack metabolism and depend on functions of the host cells for propagation.<ref>{{cite journal |last1=Grada |first1=Ayman |last2=Mervis |first2=Joshua |last3=Falanga |first3=Vincent |title=Research Techniques Made Simple: Animal Models of Wound Healing |journal=Journal of Investigative Dermatology |date=October 2018 |volume=138 |issue=10 |pages=2095–2105.e1 |doi=10.1016/j.jid.2018.08.005 |pmid=30244718 |doi-access=free }}</ref>

In [[eukaryote]]s, several yeasts, particularly ''[[Saccharomyces cerevisiae]]'' ("baker's" or "budding" yeast), have been widely used in [[genetics]] and [[cell biology]], largely because they are quick and easy to grow. The [[cell cycle]] in a simple [[yeast]] is very similar to the cell cycle in [[human]]s and is regulated by [[homology (biology)|homologous]] proteins. The fruit fly ''[[Drosophila melanogaster]]'' is studied, again, because it is easy to grow for an animal, has various visible congenital traits and has a [[polytene]] (giant) chromosome in its salivary glands that can be examined under a light microscope. The [[roundworm]] ''[[Caenorhabditis elegans]]'' is studied because it has very defined development patterns involving fixed numbers of cells, and it can be rapidly assayed for abnormalities.<ref>{{Cite journal |last1=Duina |first1=Andrea A. |last2=Miller |first2=Mary E. |last3=Keeney |first3=Jill B. |date=May 2014 |title=Budding Yeast for Budding Geneticists: A Primer on the Saccharomyces cerevisiae Model System |journal=Genetics |volume=197 |issue=1 |pages=33–48 |doi=10.1534/genetics.114.163188 |issn=0016-6731 |pmc=4012490 |pmid=24807111}}</ref>