Advancing Epigenetics Towards Systems Biology

What is chromatin, euchromatin and heterochromatin?

Chromatin is the molecular substance of a chromosome. It consists of a complex of DNA, RNA and protein in eukaryotic cells. Frequently, people encounter pictures of chromosomes which have a striped pattern of stronger and lighter staining. What are these chromosome bands? Do they represent genes? No, they do not necessarily represent genes nor do they automatically correspond to stretches lacking genes. Chromosomes often presented to the public are most highly compacted metaphase chromosomes or the giant chromosomes (i.e. polytene chromosome) of Drosophila larvae from salivary gland cells. The latter are made up of about 2000 DNA double strands arranged parallel to each other. A single band of a Drosophila giant chromosome can contain about 50.000 nucleotides in a row. But what makes its staining different to an adjacent band? What we see as dark bands is a consequence of an increased concentration of DNA within variably, compacted chromatin that differs in staining on average every 50 kb. But there is also a gradient of diverse higher order degrees of compaction. Further, in the life of a chromosome it alters its appearance. During the so-called interphase it is relaxed with a lot of open chromatin (see FAQ 7). During this phase, some entire chromosomes but mostly only parts thereof retain a strong staining. These subnuclear features are known since the early days of cytology. In 1928, Heitz introducd for them the term 'heterochromatin'. Euchromatin, on the other hand, is highly decondensed chromatin. Chromosomal regions in the genome which lack high numbers of genes are normally compacted in heterochromatin while chromosomal regions with high concentrations of transcribed genes are part of relaxed euchromatin. But these patterns change during development depending on the pattern of particular epigenetic tags present in the chromatin (see FAQ 8).

Mon, May 29th 2017- Wed, May 31st 2017

After last year's successful kick-off meeting, the EpiGeneSwiss meeting will take place again in Weggis, Switzerland. This year we have added one day in addition to accommodate more topics and more t...

Mon, Jun 19th 2017- Wed, Jun 21st 2017

The focus of the 2017 IMB Conference is on “Gene Regulation by the Numbers: Quantitative Approaches to Study Transcription”. The conference will explore the latest findings and technological developme...

Tue, Jul 11th 2017- Thu, Jul 13th 2017

The MRC Integrative Epidemiology Unit at the University of Bristol invites all professionals interested in aetiological epidemiology and Mendelian randomization to attend our conference on the subject...

Wed, Aug 30th 2017- Fri, Sep 1st 2017

The nucleosome is the fundamental building block of chromatin organisation and genome function. The 20th anniversary of the high resolution nucleosome structure marks a milestone for bringing together...


EpiGeneSys Final
Meeting in Paris

Thur. 11 February 2016 - Sat. 13 February 2016

More than 280 scientists attended the fifth Annual Meeting of EpiGeneSys. The conference kicked off with a talk by coordinator Geneviève Almouzni, Director of the Research Center at the Institut Curie, highlighting the achievements of the network over more than five years...

Maison des océans - Paris Read more


The Non-Coding Genome ...

December 3-4 th, 2015

The last training workshop of the EpiGeneSys network

Hotel Mediterraneo - Rome, Italy Read more

Paris / TriRhena Chromatin Club

July 9th, 2015

...exciting talks and network with members of the Chromatin community!

... An EpiGeneSys TAB workshop

June 11st-12nd , 2015

... learn about current approaches to single cell epigenetics and to meet up and network with...

Montpellier, FranceRead more

Latest publications


The impact of rare and low-frequency genetic variants in common disease.

Read more

Stable Polycomb-dependent transgenerational inheritance of chromatin states in Drosophila.

Read more

Stable Polycomb-dependent transgenerational inheritance of chromatin states in Drosophila.

Read more