Chromatin is the material inside the cell nucleus made of DNA and proteins (primarily Histone proteins). Chromatin packs the DNA into small volumes to adjust in the cell. It strengthens the Deoxyribonucleic Acid (DNA) for mitosis and meiosis. It also controls replication, and gene expression and saves DNA from damage. Euchromatin and heterochromatin are both types of chromatin.
Heterochromatin and Euchromatin are chromatin, yet different in their form and structure. Euchromatin is the active chromatin inside the nucleus, whereas heterochromatin is the inactive form of chromatin. Let’s discuss the differences between Euchromatin and heterochromatin in detail.
Comparison Table
| Factor | Euchromatin | Heterochromatin |
| Presence | Eukaryotes/prokaryotes | Eukaryotes |
| Location | Centre of the cell | Cell’s periphery |
| Structure | Beaded structure | Compact structure |
| Function | Transcription, and gene variation | Genome structure, and gene regulation |
| Genetic process influence | Yes | No |
| Genome content | 90% in humans | 8-10% in humans |
| Stickiness | No such regions | Sticky |
| Staining | Lightly stained | Dark stained |
| Examples | Most chromosomes | Genes 1, 9, 16 |
What is Chromatin?
As mentioned earlier, chromatin is the genetic material inside the nucleus, made of DNA and proteins. DNA carries genetic information, while proteins help bind the genetic material into a compact form to fit in the nucleus. Chromatin is the unwound form of chromosomes that packages to create chromosomes at the time of division. The two chromatin types are:
- Euchromatin
- Heterochromatin
What is Euchromatin?
According to the name, Euchromatin, the “true chromatin” is loosely packed and actively involved in transcription to produce mRNA. The structure of Euchromatin and nucleosomes is alike, with 147 DNA base pairs wrapped around the histone proteins. The loosely bound DNA enables quick transcription due to its immediate availability.
The gene-regulating mechanism makes it possible to transform heterochromatin into Euchromatin and vice versa. Euchromatin is involved in transcription by using active genes and helps encode functional proteins. Euchromatin is said to contain 90% of the total human genome.
What is Heterochromatin?
On the other hand, heterochromatin is the highly compact and dense chromatin that prevents RNA and DNA polymerase, and other proteins from finding their way to the DNA. Heterochromatin is only present in the nucleus of eukaryotes to help in replication. Heterochromatin is of two types, facultative and constitutive heterochromatin.
The facultative heterochromosomes are inactive genes and are not a permanent feature of all cell nuclei. They form through the process of siRNA or Histone methylation. Alternatively, constitutive heterochromatin makes the repetitive, functional genes like centromeres and telomeres. They are the continuing nature of the nucleus and retain their structure during the interphase of cell division.
Difference between Euchromatin and Heterochromatin
Definition
Euchromatin
Euchromatin is the loosely packed form of DNA, containing different segments of genes, in the nucleus and transcription.
Heterochromatin
Heterochromatin is tightly packed DNA present in the nucleus and is transcriptionally inactive.
Presence
Euchromatin
Euchromatin is found in the nucleus of both prokaryotes and eukaryotes.
Heterochromatin
Though you can only see heterochromatin in eukaryotic organisms.
Location
Euchromatin
Euchromatin is more widely found in the center or inner body of the nucleus.
Heterochromatin
Yet, it is more prominent along the periphery of the cell nucleus.
Structure
Euchromatin
The DNA forms a loose beaded structure within the nucleus to fit well.
Heterochromatin
However, the DNA is wrapped around a structural protein, called histone protein to form a compact structure.
Function
Euchromatin
Euchromatin enables the process of transcription and gene-variation occurring within the genes.
Heterochromatin
In contrast, it is responsible for maintaining the structure of the genome and gene expression regulation.
Activity
Euchromatin
Euchromatin is transcriptionally active and involved in transcription.
Heterochromatin
Contradictorily, heterochromatin is not involved in transcription and is transcriptionally inactive.
Genetic Process Influence
Euchromatin
Euchromatin is affected by numerous genetic processes like position-effect variegation.
Heterochromatin
Conversely, none of the genetic processes occurring in the cell affect heterochromatin.
Genome Content
Euchromatin
Euchromatin makes up most of the human genome, consisting of around 90% of the total.
Heterochromatin
Whereas heterochromatin makes a smaller part of the genome, making around 8 – 10% of the human genome.
Stickiness
Euchromatin
Euchromatin does not have sticky regions in the structure.
Heterochromatin
Alternatively, heterochromatin is different than Euchromatin and has some sticky regions.
Staining
Euchromatin
Euchromatin appears as the lightly stained type of chromatin.
Heterochromatin
When observed under a microscope, heterochromatin appears to be darkly stained.
Examples
Euchromatin
All types of chromosomes in a genome are examples of Euchromatin besides heterochromatin.
Heterochromatin
Some of the heterochromatin present in the genome are genes 1, 9, and 16.
FAQs
How does the euchromatin look under a microscope?
You cannot see hetero and euchromatin distinctly under a student microscope. However, when you observed chromatin under the compound or electron microscope. Heterochromatin is darkly stained, loosely packed chromatin, while Euchromatin is comparatively lightly stained.
What does the chromatin turn into?
Chromatin folds into specific formations called chromosomes, having DNA strands and proteins. They contain the genetic material of the cell and are involved in cell division.
How much chromatin does each chromosome have?
Each chromatin forms one chromosome, which means that every chromosome has one chromatin.
What are the components of chromatin?
Chromatin is primarily made of histone proteins, DNA and RNA. Sometimes students wonder if it contains lipids; no, lipids are not a component of chromatin.
Is chromatin present in bacteria?
Chromatin is not present in bacteria in the same shape as eukaryotes. However, it forms a membrane-free region commonly known as the nucleoid that modifies shape according to the bacterial state.
The Bottom Line
Heterochromatin and Euchromatin are both types of chromatin and important parts of the cell. While Euchromatin is involved in transcription directly, heterochromatin maintains the genome structure. Most of the human genome contains Euchromatin found in prokaryotic and Eukaryotic cells. However, heterochromatin contributes to 10% of the genome and is only present in eukaryotes. When you observe both under a microscope, Euchromatin occurs as a lightly stained threadwork while heterochromatin is stained dark.
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