DNA and Chromatin structure
Contents
The functions of chromatin are to package DNA into a smaller volume to fit in the cell (1.8meter of DNA into a nucleus with a diameter of 6 um), to enable mitosis and meiosis, and to serve as a mechanism to control expression and DNA replication.
Overview
The organization of DNA in its cell nucleus is an extremely complex 3-dimensional architecture of a number of different structures, from the simple sugar-phosphate chain to the highly condensed mitotic chromosomes.
Chromatin is the complex combination of DNA, RNA, and protein that makes up chromosomes. It is divided between heterochromatin (condensed) and euchromatin (extended) forms. The major components of chromatin are DNA and histone proteins, although many other chromosomal proteins are present and with distinct roles too. The functions of chromatin are to package DNA into a smaller volume to fit in the cell (1.8meter of DNA into a nucleus with a diameter of 6 um), to enable mitosis and meiosis, and to serve as a mechanism to control expression and DNA replication. Changes in chromatin structure are affected by DNA binding proteins and by chemical modifications such as methylation and acetylation.
Normal differentiation relies on a stringent transcription control system with a continual process of activation and deactivation of the different genes. It is generally recognised that chromatin structure regulate DNA function within the cell, and the overwhelming evidence for rearrangements of the genetic material in tumours, combined with the present knowledge of chromatin structure and function, support the view that cancer is a disease also of DNA organisation.
Chromatin may be studied on many different levels. Our approach is to study chromatin as it is visualized in the interphase nuclei under a microscope (chromatin literally means coloured lightend material). Our methods are based upon computer-assisted image analysis, where images of cell and tissue samples are transferred from the microscope (light-, laser- and electron microscopy) to the computer. The digital images of chromatin permits us to study the structure and organization of DNA bit by bit by use of advanced texture analysis. We refer to these methods as Nucleotyping.