Chromatin structure plays a pivotal role in transcriptional control. In histology, the state of chromatin (euchromatin or heterochromatin) determines the accessibility of transcription factors to DNA. Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and transcriptionally silent. Modifications such as acetylation and methylation of histone proteins can alter chromatin structure and, consequently, gene expression.
