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Unraveling the genetic basis of hybrid vigor

Division of Biological Sciences, University of Missouri, Columbia, 65211, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 09/2006; 103(35):12957-8. DOI: 10.1073/pnas.0605627103
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Available from: James A Birchler, Jul 28, 2015
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    • "A third genetic model, referred to as " pseudo-overdominance, " is actually a simple case of dominance complementation in which the two genes are linked and the increasing alleles are inherited in repulsion, i.e. each parent contributes one of the two increasing alleles at two different but genetically linked genes to the hybrid. This type of complementation in the hybrid resembles overdominance , because of the tight chromosomal linkage and the co-inheritance of these genes as a single one [1]. In fact, distinction between the overdominance and dominance models should give an indication of how much the specific heterozygosity, as opposed to overall heterozygosity (proportional to the genetic distance between parents of the hybrids), causes heterosis. "
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    • "If overdominant loci are common, they should cause substantial reductions in fitness when organisms are inbred, and indeed, inbreeding depression is very common (Charlesworth & Charlesworth , 1987). However, data returning from long-term genetic studies of corn began to suggest that heterosis is caused more by pseudo-overdominance than genuine heterozygote advantage (Gardner, 1963; Moll et al., 1964; Crow, 1987; but also see Birchler et al., 2006). Here, pseudo-overdominance refers to elevated fitness in hybrids owing to complementation of recessive deleterious alleles at two closely linked genes (see Table 1 for definitions of some relevant terms). "
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    • "bred parents in more than one dimension ; for example , the hybrid may have an extended period of expres - sion , broader spatial distribution , or more adapted environ - ments than its inbred parents . The cumulative effects from such an allelic diversity may result in an overall non - allelic additive effect on hybrid performance and heterosis ( Birchler et al . 2006 ) . Vergeer et al . ( 2012 ) have recently provided intriguing results that may change our understanding of inbreeding depression and challenge the classical theory of how inbreeding depression evolves , and might give us clues to further studies ; the details are discussed in " Regulatory mechanism of ASE " ."
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