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A postzygotic mutation (or post-zygotic mutation) is a change in an organism's genome that is acquired during its lifespan, instead of being inherited from its parent(s) through fusion of two haploid gametes. Mutations that occur after the zygote has formed can be caused by a variety of sources that fall under two classes: spontaneous mutations ...
In others, normal segmentation occurs in the blastula but gastrulation fails. Finally, in other crosses, the initial stages are normal but errors occur in the final phases of embryo development . This indicates differentiation of the embryo development genes (or gene complexes) in these species and these differences determine the non-viability ...
[3]: 362 Coyne and Orr surveyed 171 species pairs, collecting data on their geographic mode, genetic distance, and strength of both prezygotic and postzygotic isolation; finding that prezygotic isolation was significantly stronger in sympatric pairs, correlating with the ages of the species.
[3]: 354 [4] [5] Differences in behavior or biology that inhibit formation of hybrid zygotes are termed prezygotic isolation. Reinforcement can be shown to be occurring (or to have occurred in the past) by measuring the strength of prezygotic isolation in a sympatric population in comparison to an allopatric population of the same species.
Postzygotic incompatibilities - reproductive barrier arising after zygote formation, including inviability and sterility. Post-mating barriers - Reproductive barriers that act after mating. These can include barriers that act after mating but before the zygote is formed (Post-mating, pre-zygotic barriers).
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Hybrid inviability is a post-zygotic barrier, which reduces a hybrid's capacity to mature into a healthy, fit adult. [1] The relatively low health of these hybrids relative to pure-breed individuals prevents gene flow between species.
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