In population genetics, a gene pool is the complete set of unique alleles in a species or population.
Description
A large gene pool indicates extensive
genetic diversity, which is associated with robust populations that can survive bouts of intense
selection. Meanwhile, low genetic diversity (see
inbreeding and
population bottlenecks) can cause reduced
biological fitness and an increased chance of
extinction, although as explained by
genetic drift new genetic variants, that may cause an increase in the
fitness of organisms, are more likely to fix in the population if it is rather small.
When all individuals in a population are identical with regard to a particular phenotypic trait, the population is said to be monomorphic. When the individuals show several variants of a particular trait they are said to be polymorphic.
Gene pool concept in crop breeding
Harlan and de Wet (1971) proposed classifying each crop and its related species by gene pools rather than by formal taxonomy.
#Primary gene pool (GP-1): Members of this gene pool are probably in the same "
species" (in conventional biological usage) and can intermate freely. Harlan and de Wet wrote, "Among forms of this gene pool, crossing is easy;
hybrids are generally fertile with good chromosome pairing; gene segregation is approximately normal and gene transfer is generally easy."
. They also advised subdividing each crop gene pool in two:
#*Subspecies A: Cultivated races
#*Subspecies B: Spontaneous races (wild or weedy)
#Secondary gene pool (GP-2): Members of this pool are probably normally classified as different species than the crop species under consideration (the primary gene pool). However, these species are closely related and can cross and produce at least some fertile hybrids (F1s). As would be expected by members of different species, there are some reproductive barriers between members of the primary and secondary gene pools:
#*hybrids may be weak
#*hybrids may be partially sterile
#*
chromosomes may pair poorly or not at all
#*recovery of desired
phenotypes may be difficult in subsequent generations
#*However, "The gene pool is available to be utilized, however, if the plant breeder or geneticist is willing to put out the effort required."
#Tertiary gene pool (GP-3): Members of this gene pool are more distantly related to the members of the primary gene pool. The primary and tertiary gene pools can be intermated, but
gene transfer between them is impossible without the use of "rather extreme or radical measures"
such as:
#*embryo rescue (or embryo culture, a form of plant
organ culture)
#*induced
polyploidy (chromosome doubling)
#*bridging crosses (e.g., with members of the secondary gene pool).
See also
Biodiversity
Conservation biology
Founder effect
Gene flow
Genetic drift
Small population size
References
External links
Gap Analysis Portal reliable information source on where and what to conserve ex-situ, for crop genepools of global importance
Category:Ecology
Category:Conservation
Category:Selection
Category:Classical genetics
Category:Population genetics
Category:Evolutionary biology
![A Bengal tiger in a national park in southern India. Indian officials successfully reintroduced two Bengal tigers in the Sariska Tiger Reserve in July 2008.[103]](http://web.archive.org./web/20110130191640im_/http://cdn.wn.com/pd/a8/39/be0d1bb5a8dbc759b4ebf27d3d2a_grande.jpg "A Bengal tiger in a national park in southern India. Indian officials successfully reintroduced two Bengal tigers in the Sariska Tiger Reserve in July 2008.[103]")
![A Bengal tiger in a national park in southern India. Indian officials successfully reintroduced two Bengal tigers in the Sariska Tiger Reserve in July 2008.[103]](http://web.archive.org./web/20110130191640im_/http://cdn.wn.com/pd/a8/39/be0d1bb5a8dbc759b4ebf27d3d2a_thumb.jpg "A Bengal tiger in a national park in southern India. Indian officials successfully reintroduced two Bengal tigers in the Sariska Tiger Reserve in July 2008.[103]")
