Microphotometrical scanning and computer graphic image analysis were carried out to detect the distribution of chromatin densities in subtelomeric segments of T-banded endoreduplicated chromosomes of Chinese hamster ovary (CHO) cells. Chromatin density patterns detected with this method were similar to those previously found in CHO and normal human chromosomes. The highest chromatin densities were considered as marker segments which led to the detection of reciprocal changes of position in endoreduplicated chromosomes during cell spreading on the slide. The problem of the subtelomeric T-banding density patterns found in the endoreduplicated chromosomes and their relation to the structure and molecular composition of this region is briefly discussed.
