| Criteria | Euchromatin | Heterochromatin | Remarks |
| Chromatin packing | Relatively loosely packed | Highly condensed and tightly packed | Determines accessibility of DNA |
| Staining | Lightly stained | Darkly stained | Heterochromatin retains more stain because of its compact structure |
| DNA accessibility | Highly accessible to transcription factors and other DNA-binding proteins | Relatively inaccessible | Accessibility strongly influences gene activity |
| Transcriptional activity | Generally transcriptionally active | Generally transcriptionally inactive or less active | Euchromatin contains many actively expressed genes |
| Gene density | Usually gene-rich | Usually gene-poor | Exceptions exist |
| DNA replication | Replicates relatively early during S phase | Usually replicates late during S phase | Replication timing reflects chromatin organization |
| Nucleosome organization | More dynamic and accessible | More compact and stable | Nucleosome positioning affects DNA accessibility |
| Histone modifications | Often enriched in activating marks such as H3K4me3 and histone acetylation | Often enriched in repressive marks such as H3K9me3 and H3K27me3 | Histone modifications help establish chromatin states |
| DNA methylation | Generally lower at active gene promoters | Often higher, particularly in repetitive and silenced regions | DNA methylation is associated with transcriptional repression |
| Typical genomic regions | Many gene-rich regions and actively transcribed genes | Centromeres, telomeres, and many repetitive DNA regions | Distribution varies across chromosomes |
| Chromosome position | Frequently found in more open, chromosome-arm regions | Commonly enriched around centromeres and telomeres | Some heterochromatin also occurs within chromosome arms |
| Types | Generally considered a more uniformly open chromatin state | Constitutive and facultative heterochromatin | Facultative heterochromatin can switch between active and inactive states |
| Examples | Actively expressed housekeeping and tissue-specific genes | Centromeric repeats and silenced genomic regions | The same genomic region can change its chromatin state |
| Main biological role | Facilitates gene expression and DNA-related processes | Maintains genome stability and regulates gene silencing | Both are essential for normal genome organization and function |
| Cellular dynamics | Relatively dynamic and can become more or less compact | Generally more stable, although some regions are reversible | Chromatin states can change during development and differentiation |
