Answer:
The formation of one isochromosome
Step-by-step explanation:
In cytogenetics, an isochromosome is a structurally abnormal chromosome that renders two chromosome arms which are identical inverses of each other. An isochromosome is caused by simultaneous duplication and deletion of genetic information during DNA replication. The resulting isochromosome will contain two identical copies of either the long or short chromosome arms that are disposed as a mirror image.