Poe, Journalist and Critic

The "Condensation-Decondensation" of Chromatin as Related to Chromosomal Structure: A System Examining Various Conditions Affecting Fractionation of Chromatin

“…This thought was developed from previous observa tions that condensation induces specific conformational chan ges in the chromatin complex, and that this condensation results in restriction of the accessibility of the coding elements of the DNA not only to macromolecules but also to relatively small molecules such as acri di ne orange or actinomycin D (166,170). Condensed chromatin can be dispersed, with a concomitant increase in its ability to bind inter calating dyes, not only by removal of basic proteins, but also by changes in the ionic environment (174,172). Both in the intact cell and in isolated nuclei, chromatin exhibits a marked sensitivity to the electrolyte composition of the environmental medium (172); and reversible condensation or dispersion can be produced by changes in the concentrations of either divalent or monovalent cations (172).…”

“…The effect of ionic strength on the degree of condensa tion of chromatin from interphase nucleus has been studied by viscocity (65,135,174), sedimentation velocity (174,175), thermal denaturation (26,65), optical absorbance (47,147,176), titration (93), and electron microscopy (177). Studies with giant chromosomes from the salivary glands of Chironomus have -Illconcluded that the changes in ionic strength can effect the architecture of metaphase chromatin (178)(179)(180).…”