iGen3 16-09

Pericentric Chromosome Inversion: effect on crossover products

A pericentric ("around the center") inversion includes the centromere (o). In the example, the BCoD region of the standard chromosome ABCoDEFGH has been inverted, to give the locus order A(DoCB)EFGH. After chromatid duplication in meiosis, the paired inverted chromosome forms a loop so that the loci pair with their homologous on the uninverted chromosome.

Occurence of a crossover event inside the loop produces four types of products in the gametes: two chromosomes with the standard and inverted gene order, and two duplication / deletion products in which one or more loci have been duplicated or deleted, according to where the crossover has occured with respect to the inverted region.

Note that, unlike a paracentric inversion, all gene loci are represented in the final products, and only the order of loci is changed. In the final set of fragments, count the number of A B C D  E F G H loci.

Figure © 2010 PJ Russell, iGenetics 3rd ed.; all text material ©2014 by Steven M. Carr