Here's why:

* Chromatin: Chromatin is the complex of DNA and proteins (histones) that makes up chromosomes. It's found in the nucleus of eukaryotic cells.

* Coiling and Uncoiling: The degree of coiling in chromatin affects how accessible the DNA is for transcription.

* Tightly coiled chromatin (heterochromatin): DNA is tightly packed and inaccessible to transcription factors, so genes within this region are usually inactive.

* Loosely coiled chromatin (euchromatin): DNA is more accessible, allowing transcription factors to bind and initiate gene transcription.

In short: The coiling and uncoiling of chromatin acts like a switch, controlling whether a gene is turned on or off.