Morphology alone does not make an isochromosome

Abstract
Isochromosomes are chromosomes with genetically identical arms. Chromosomes morphologically similar to isochromosomes can arise from alternative mechanisms: wholearm translocations and crossing over within inversion loops. Cases are presented which could have arisen by each of these latter two mechanisms. The first case is 46,XX,t(15;15) (qtercen-qter; pter-cen-pter) and the second 46,XY,rec(18), dup q,inv(18)(p11.32q11.2).