(D) Organization of inactive chromatin
Chromatin is composed of DNA, RNA, and protein. In routine H&E slide preparations, nuclear chromatin binds hematoxylin and is said to be basophilic. Patterns of gene expression are regulated, in part, by global changes in chromatin packing. Inactive chromatin, heterochromatin, is highly condensed and deeply basophilic. Much of the heterochromatin in this endothelial cell is found along the periphery of the nucleus. This is referred to as marginal chromatin. By contrast, active chromatin, euchromatin, is dispersed within the nucleoplasm and lightly stained. Chromatin is supported and organized by structural pro- teins that provide points of attachment between chroma- tin and the inner nuclear membrane. None of the other cell processes describe the function of heterochromatin.