The ultrastructure of cold-modified segments of metaphase chromosomes

Abstract

Cold-modified segments ofTrillium mitotic metaphase chromosomes were observed with the electron microscope and found to consist of fibrils 8–9 nm in diameter and fibrils 10–20 nm in diameter. Both types of fibrils were organized into coarser thread-like units, 0.1–0.5Μm in diameter. These observations were interpreted as being consistent with the hypothesis that the cold-induced negatively heteropyknotic regions of Feulgen stained chromosomes observed with light microscopy are where the chromatin failed to undergo the typical condensation prior to metaphase.