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Difference Between Euchromatin And Heterochromatin

Euchromatin-And-Heterochromatin

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

FactorEuchromatinHeterochromatin
PresenceEukaryotes and prokaryotesEukaryotes
LocationCentre of the cellThe periphery of the cell
StructureBeaded structureCompact structure
FunctionTranscription, gene variationGenome structure, gene regulation
Genetic process influenceYesNo
Genome content90% in humans8-10% in humans
StickinessNo sticky regionsSticky
StainingLightly stainedDark stained
ExamplesMost chromosomesGenes 1, 9, 16

What is Chromatin?

As mentioned earlier, chromatin is the genetic material inside the nucleus, made of DNA and proteins. DNA carries the genetic information, while the proteins help bind the genetic material into a compact form to fit in the nucleus. Chromatin is the unwound form of chromosomes that package 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. 

Euchromatin-structure

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. 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.

Heterochromatin-structure

Difference between Euchromatin and Heterochromatin

Definition

Euchromatin 

Euchromatin is the loosely packed form of DNA 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 the histone proteins 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.

Heterochromatin-and-Euchromatin-connection

FAQs

How does the euchromatin look under a microscope?

When observed under a microscope, the 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. 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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