A Robertsonian Type of Chromosomal Change in L4946 Mouse Ascites Lymphoma2

Abstract
L4946 ascites lymphoma of AKR mice had maintained the karyotype consisting of 41 acrocentric chromosomes for 18 months in our laboratory. Suddenly a large mediocentric chromosome and a heterochromatic minute were formed, apparently at the expense of two acrocentric chromosomes, providing a classic example of a Robertsonian relationship manifesting itself within the neoplastic cell population of a transplantable tumor. The sensitivity to breakage of centromeric heterochromatic regions of the acrocentric chromosomes has been considered as a cause of this type of karyological evolution.