Nucleus – Structure and Function Practice Test

Staining differences here come from how tightly the DNA is packed. Heterochromatin is highly condensed, so it packs more DNA and associated proteins into a small space and takes up more dye, appearing dark under standard light microscopy. Euchromatin is less condensed and more transcriptionally active, with less dense DNA, so it binds dye less and looks lighter. That’s why the statement describing heterochromatin as darkly stained and euchromatin as lightly stained best fits what is observed. The other options misstate the pattern or add inaccurate ideas, like no staining difference or an absolute, never-mixing separation.