What is chromatin made of

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Chromatin is the basic genetic material in our cell nuclei. It consists of DNA (deoxyribonucleic acid) and associated proteins (proteins). The name chromatin is derived from the Greek word “chroma” (= color), because chromatin can be colored. Find out everything you need to know about chromatin here: definition, structure, function and possible health disorders!

What is chromatin?

Chromatin is the entirety of all thread-like units of the genetic material within the cell nucleus, which are made up of deoxyribonucleic acid (DNA) and special proteins (especially histones):

The long, chain-shaped DNA carries the genetic information of an organism. It is found in the cell nucleus in several double-stranded “threads”. Each DNA thread is wrapped around an eight-part group (octamer) of histone proteins at certain intervals and thus “condensed”, that is, shortened or packaged (this is how it first fits into the cell nucleus). A single histone complex and the part of DNA that is spiraled around it is called a nucleosome.

Chromosomes

Overall, the chromatin appears under the microscope as a blurred, loosened, amorphous mass in the cell nucleus. In this form, the genetic material exists between two successive cell divisions (interphase).

If the cell wants to divide, however, the chromatin must first be converted into a “transport form”: the individual DNA threads are “packed” (condensed) even more tightly until they are available as compact chromosomes. These are more visible under the microscope than the loosened chromatin.

Barr body

Women have two X chromosomes as sex chromosomes. One of them is inactivated and lies in many cells as a small, strongly condensed Barr body (sex or sex chromatin) on the edge of the cell nucleus.

This fact is used in the so-called Barr test. It is used to determine gender in unclear cases, for example in people with hermaphroditism - they have both testicular and ovarian tissue.

For the test, for example, epithelial cells are taken from the person's oral mucosa and see whether Barr bodies can be found in these. If this is the case with a certain percentage of the cells, the person is considered to be female.

What is the function of chromatin?

The chromatin function is based on the DNA it contains: This contains the blueprints for all proteins in the body. Not all of this information is needed in a cell. That is why chromatin exists in two organizational states - as euchromatin and as heterochromatin:

  • The Euchromatin is loosened and easily accessible so that the information stored in the DNA segments can be "read" and used for protein synthesis (transcription). So these are active DNA segments.
  • In the case of the more compact heterochromatin, on the other hand, “reading” is not possible; the contained DNA segments are inactive.

Where is chromatin located?

Chromatin is found in the cell nuclei of humans, animals and higher plants.

What problems can chromatin cause?

Structural errors in chromatin can influence the activity pattern of the DNA and thus cause rare and sometimes very serious diseases.

One example is Coffin-Siris Syndrome (CSS): This rare congenital disease is associated with delayed development, intellectual disability and rough facial features, among other things. In people with this chromatin disease, the terminal phalanx of the little finger or its nail is also underdeveloped or nonexistent.

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