Difference Between Euchromatin And Heterochromatin

The major difference between Euchromatin and Heterochromatin is that euchromatin is an uncoiled packed and genetically active form of chromatin. While heterochromatin is a firmly packed form and is a genetically inactive part of the chromosomes.

The non-dividing cells of the nucleus exhibit the two regions, on the ground of concentration or intensity of staining under the light microscope. After the observation, the darkly stained region found under the light microscope is known as heterochromatin and a lightly stained region is known as euchromatin.  The main function of euchromatin is to protect the DNA in the genome present in the nucleus. Approximately, 90% of the total human genome is euchromatin and are the parts of chromatin.

Difference Between Euchromatin And Heterochromatin

Let us understand the key difference between euchromatin and heterochromatin.

Character	Euchromatin	Heterochromatin
Definition	Euchromatin is a more lightly packed DNA that is characterized by less enormous staining and DNA sequences that are transcriptionally active or might become transcriptionally-active at some point during growth.	Heterochromatin is a firmly packed or condensed DNA that is characterized by enormous stains when stained with nuclear stains and transcriptionally inactive sequences.
DNA conformation	The DNA is compressed and unfolded to form a beaded structure.	The DNA is condensed and folded with the histone proteins.
Transcription	It is transcriptionally-active.	It is transcriptionally-inactive.
Staining	It is lightly stained under nuclear stains.	It is darkly stained under nuclear stains.
Genes	The genes found in this are either already active or will be active during growth.	The genes found in this are usually inactive.
DNA content	Euchromatin consists of less amount of DNA lightly compressed with the histone proteins.	Heterochromatin consists of more amount of DNA tightly compressed with the histone proteins.
Found in	Euchromatin is present in both prokaryotes and eukaryotes.	Heterochromatin is present only in eukaryotes.
Content in genome	It forms a more significant part of the genome. In humans, it is approximately 90-92% of the genome.	It forms a smaller part of the genome. In humans, it is approximately 8-10% of the genome.
Location	Euchromatin is found in the inner body of the nucleus.	Heterochromatin is found towards the periphery of the nucleus.
Heteropycnosis	Euchromatin doesn’t indicate heterozygosis.	Heterochromatin indicates heterozygosis.
Function	Euchromatin allows the transcription and variation of the gene to occur within the genes.	Heterochromatin maintains the structural integrity of the genome and allows the regulation of gene expression.
Replicative	It is an early replicative and replicates earlier than heterochromatin.	It is a late replicative and replicates later than euchromatin.
Genetic processes	It is affected by various genetic processes.	Heterochromatin is not affected by genetic processes.
Types	It consists of a single type; constitutive euchromatin.	It consists of two types; constitutive and facultative heterochromatin.
Examples	All the chromosomes in the genome except the heterochromatin are examples of euchromatin.	Telomeres and centromeres, one of the X chromosomes, genes 1, 9, and 16 of humans, Barr bodies, are some examples of heterochromatin.

Euchromatin

Definition

Euchromatin is defined as a loosely packed form of chromatin. It is a part of chromosomes, which is rich in gene concentrations. Euchromatin is highly active during transcription.

Euchromatin consists of approximately 90% of the entire human genome. It covers the maximum part of the dynamic genome to the inner of the nucleus.

The structure of euchromatin is similar to the nucleosomes, which includes the histones proteins having about 147 base pairs of DNA wrapped around them. To let the transcription happen, some parts of the genome which consist of active genes are loosely packed. The DNA wrapped around them is so loose that it can become readily available.

Euchromatin actively takes part in the transcription from DNA to RNA. The gene-regulating mechanism is the process in which the euchromatin is transformed into heterochromatin or vice versa. Housekeeping genes are said to be one of the forms of euchromatin.

The active genes present in euchromatin are used in the transcription to make mRNA. While the main function of the euchromatin is to further encode the functional proteins. Hence they are contemplated as genetically and transcriptionally active.

Heterochromatin

Definition

Heterochromatin is defined as the enormously stained region of the chromosomes with DNA-specific strains and is relatively condensed. They are the firmly packed form of DNA in the nucleus.

The structuring of heterochromatin is so highly compact that these are very hard to get access to the protein which is engaged in gene expression. Due to the above reason, it becomes difficult to perform the chromosomal cross over. Hence, the heterochromatin is transcriptionally as well as genetically inactive.

Types

Heterochromatin is further characterized into two types

Facultative Heterochromatin

The facultative heterochromatin is defined as the genes which get still through the process of Histone methylation or siRNA through RNAi. Hence they consist of the inactive genes and are considered as not a permanent character of every nucleus of the cells.

Constitutive Heterochromatin

Constitutive heterochromatin is defined as the repetitive and structurally functional genes like telomeres or centromeres. During the interphase of the cell, the structure of constitutive heterochromatin is capable to retain. They do not contain any gene in the genome. They are also described as the continuing nature of the cell’s nucleus.

Function

The main function of heterochromatin is to secure the DNA regions to get accessed to proteins during gene expression. Due to its compact nature, heterochromatin also prevents the DNA from endonuclease damage.

Conclusion

From the above information regarding the structure and types of chromatin. It is observed that only Euchromatin is strongly involved in the transcription process. While heterochromatin and its types do not play such an important role.

Constitutive heterochromatin surrounds the centromere, and facultative heterochromatin is disbanded and contains the satellite DNA. So apparently it concludes that the eukaryotic cells and their inner structure are relatively complex.