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.