Geneticists have identified certain model
organisms which are useful for studying genetic processes in cells. Among the
bacteria, E. coli, which is commonly found in the mammalian intestinal
tract, has been one of the most widely studied species due to its genetic
simplicity and the ease with which it may be grown in the laboratory. Bacillus
subtilis, typically found in soil environments, has also been intensively
studied because of its tolerance for genetic modification and its ability to
produce commercially available biochemicals. Among plants, Arabidopsis
thaliana, a mustard weed, has been selected as a model organism due to
its high reproductive rate and relatively small genome size. These features
make this small weed simpler to genetically manipulate than more complex
plant species. Within the Fungi kingdom, the bread mold Neurospora crassa
has been chosen as a representative organism because its haploid genome
allows the effects of mutations in its DNA to be directly observed. In
addition, Neurospora’s short life cycle is useful for efficiently
studying patterns of genetic inheritance. Baker’s yeast, or Saccharomyces
cerevisiae, is another model organism that has been valuable to genetic
research. Yeast is an advantageous organism to study because it is a simple,
unicellular eukaryote that is easy to grow and genetically manipulate. Among
animals, the fruit fly Drosophila melanogaster is used as a model
organism mainly due to its short life cycle and high reproductive rate.
Because of these attributes, the inheritance of genetic traits and mutations
in this organism can be traced through many generations in a relatively short
period of time. Another useful animal model is the mouse. Recently developed
techniques allow scientists to breed mice with intentionally engineered
mutations in particular genes. By tracking the effect of these mutations, it
is possible to identify why certain genes are required and what functions
they serve. Finally, the worm C. elegans has been chosen as a
developmental model because it is a transparent organism where all cells are
visible when viewed under a microscope. This feature is useful because it
allows researchers to directly observe changes in the growth patterns of
individual cells. Among Archaea and extremophilic bacteria – those which grow
in extremely salty or high temperature environments - Halobacteria are good
model organisms because they are easy to culture and manipulate in the
laboratory. Furthermore, the biochemical machinery of Archaea resembles that
of eukaryotes and could therefore be useful in understanding the workings of
higher organisms.
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