Gene pool  

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-'''Sexual jealousy''' is a special form of [[jealousy]] in [[human sexuality|sexual]] relationships, present in [[animal]]s that reproduce through [[internal fertilization]], and is based on suspected or imminent [[sexual infidelity]]. It is founded on the [[instinct]] of keeping [[gene]]s in the [[gene pool]] and expecting sexual partners to care for the [[offspring]]. The concept is studied in human and non-human [[primates]] in the field of [[evolutionary psychology]].+ 
 +In [[population genetics]], a '''gene pool''' is the complete set of unique [[allele]]s 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 bottleneck]]s) can cause reduced [[fitness (biology)|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 [[polymorphism (biology)|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.<ref name= "Harlan&DeWet1971">JR Harland and JMT de Wet. 1971. Toward a Rational Classification of Cultivated Plants. Taxon 20: 509-517.</ref>
 +#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; [[hybrid]]s are generally fertile with good chromosome pairing; gene segregation is approximately normal and gene transfer is generally easy." <ref name= "Harlan&DeWet1971" />. 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 [[phenotype]]s 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."<ref name= "Harlan&DeWet1971" />
 +#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" <ref name= "Harlan&DeWet1971" /> 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 ==
 +{{Portal|Evolutionary biology}}
 +*[[Biodiversity]]
 +*[[Conservation biology]]
 +*[[Founder effect]]
 +*[[Gene flow]]
 +*[[Genetic drift]]
 +*[[Small population size]]
{{GFDL}} {{GFDL}}

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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.<ref name= "Harlan&DeWet1971">JR Harland and JMT de Wet. 1971. Toward a Rational Classification of Cultivated Plants. Taxon 20: 509-517.</ref>

  1. 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." <ref name= "Harlan&DeWet1971" />. They also advised subdividing each crop gene pool in two:
    • Subspecies A: Cultivated races
    • Subspecies B: Spontaneous races (wild or weedy)
  2. 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."<ref name= "Harlan&DeWet1971" />
  3. 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" <ref name= "Harlan&DeWet1971" /> 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

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