Dear Shaik ,

Visible changes to chromosome structure and morphology have played a very important part as indicators of genetic damage in both clinical and cancer studies.

Most of the changes encountered in clinical studies are "secondary" or "derived" aberrations. This is true also in cancer studies, except that here, there is an ongoing production of aberrations, so that in some cells, a mixture of primary and secondary changes is present, and a continuously changing karyotype

Hope it helps!!