What are the roles of model organisms in molecular biology studies? Choose two model organisms and explain your reasoning.
(do they want things like they are simple to use, relatively cheap, can be extrapolated to complex organisms, etc)…
Developing a model organisms is a tremendously expensive process, carried out by many different labs and funded from many sources over decades. Labs working with less-studied organisms may compete to draw funding and studies to their organism of interest. The funding agencies (in the USA, that’s mainly the NIH and NSF) decide where to send resources and that is where the decisions are really made as to which organisms will become model organisms. Model organisms undergo extensive studies (e.g. anatomy, physiology, development, genetics) and a detailed body of knowledge accumulates in the scientific literature. An example of a very successful and fairly recent model organism is the zebrafish. Some specialized centralized resources have been funded to support the study of zebrafish — see for instance ZIRC (the Zebrafish International Resource Center) and Zfin. (http://zebrafish.org/zirc/home/guide.php and http://www.zfin.org). To see genome information about model organisms, look at Ensembl (http://www.ensembl.org) – take a look at the "all genomes" pull-down menu on their home page.
The factors you list as important for model organisms are the sorts of factors that the funding agencies will take into consideration when deciding how to allocate resources.