Pericentric chromosome inversion:
duplication & deletion meiotic products

    The locus order in the bottom chromosome is inverted with respect to B & C: the inversion includes the centromere, and is therefore called a pericentric inversion. During meiosis, pairing of the inverted region requires that the inverted chromosome form a loop with respect to the standard chromosome. This produces duplication and deletion products, that is, chromatids that have extra loci as well as missing some.

    To prove this, start at the centromere in the topmost pair of chromatids, and trace the chromatids attached to this centromere in both directions. Note that the top chromatid has the standard arrangement of loci (ABoCD), but the second chromatid is ABoCA, that it has a duplicate A locus and lacks the D locus. Satisfy yourself that the third chromatid is DBoCD, that is, missing an A and with an extra D, the exact complement of the other duplication/deletion product.

Figure redrawn from©2002 by Griffiths et al.; all text material ©2014 by Steven M. Carr