Isochromosome
（重定向自Compound chromosome）
![Isochromosome in which the arms are mirror copies of each other.](/Images/godic/202501/05/Isochromosome2557.gif")
![Isochromosome formation through the misdivision of the centromere. Monocentric isochromosomes contain arms that are mirror images of each other.](/Images/godic/202501/05/Isochromosome_Formation2557.jpg")
An isochromosome is an unbalanced structural abnormality in which the arms of the chromosome are mirror images of each other. The chromosome consists of two copies of either the long (q) arm or the short (p) arm because isochromosome formation is equivalent to a simultaneous duplication and deletion of genetic material. Consequently, there is partial trisomy of the genes present in the isochromosome and partial monosomy of the genes in the lost arm.