Mass characteristics of DNA obtained from chromosomes of a human carcinoma cell line.

Sedimentation studies of DNA from chromosomes extracted from human mitotic cells showed that high-molecular-weight DNA can be obtained if cell hypotonic treatments and prolonged metaphase blocks are avoided. Two types of large double-stranded DNA were observed. One of these (Mr = 2.5 X 10(8)) appeared as a size class with characteristics reminiscent of the chromosomal DNA subunit hypothesis. However, this DNA is the decay product of larger molecules, whose minimum molecular weight is 6 X 10(8).