What is the Difference Between Heterochromatin and Euchromatin?

The main difference between heterochromatin and euchromatin lies in their DNA density and transcriptional activity. Here are the key differences between the two:

• Heterochromatin:
• Tightly packed form of DNA in the nucleus.
• High DNA density.
• Found only in eukaryotes.
• Inactive state, with little or no transcriptional activity.
• Typically darkly stained with DNA-specific stains.
• Examples include X chromosome inactivation in female mammals.
• Euchromatin:
• Loosely packed form of DNA.
• Low DNA density.
• Found in both prokaryotes and eukaryotes.
• Active state, participating in transcriptional activity.
• Lightly stained with DNA-specific stains.
• Contains around 90% of the entire human genome.
• Examples include housekeeping genes.

Nucleosome modifications also distinguish heterochromatin from euchromatin. Euchromatin is typically enriched in acetylated histones H3 and H4 and H3K4 methylation, whereas heterochromatin is characterized by hypoacetylation of histones, H3K9 methylation, and the association of heterochromatin protein-1 (HP1).

Comparative Table: Heterochromatin vs Euchromatin

Here is a table comparing the differences between heterochromatin and euchromatin:

Heterochromatin is a tightly packed and condensed form of DNA, while euchromatin is a more lightly packed DNA. Euchromatin is found in both prokaryotic and eukaryotic cells, whereas heterochromatin is only present in eukaryotic cells. Heterochromatin is characterized by dark staining under nuclear stains, whereas euchromatin is lightly stained. Heterochromatin has a sequence of DNA known as Line DNA, while an example of facultative heterochromatin is the inactivated female X chromosome.