The wheat Ph1 locus regulates pairing and genetic recombination during meiosis. In a genome containing related chromosome sets, appropriate pairing helps maintain regular inheritance while limiting exchange between related but nonhomologous chromosomes.
Experiments distinguish effects on chromosome synapsis from effects on the later formation of chromosomal crossovers. That distinction matters for plant breeding: increasing useful exchange need not be equivalent to removing every constraint on pairing.[ref]
Dual effect of the wheat Ph1 locus on chromosome synapsis and crossover by Azahara C. Martín and others. 2017, abstract and comparison of synapsis/crossover effects
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