A complex of macromolecules found in cells, consisting of DNA, protein, and RNA.

The proteins package and arrange the DNA and control its functions within the cell nucleus.

The composition and properties of chromatin vary from one cell type to the another, during development of a specific cell type, and at different stages in the cell cycle.

 The basic chromatin unit is the nucleosome which comprises recurrent segments of DNA wrapped around an octamer of histone proteins.

Functions of chromatin are:

1) to package DNA into a more compact, denser shape

2) to reinforce the DNA macromolecule to allow mitosis

3) to prevent DNA damage, and

4) to control gene expression and DNA replication.

The primary protein components of chromatin are histones that compact the DNA.

Found in eukaryotic cells.

Its overall structure depends on the stage of the cell cycle.

During interphase, the chromatin is structurally loose to allow access to RNA and DNA polymerases that transcribe and replicate the DNA.

The local structure of chromatin during interphase depends on the genes present on the DNA.

DNA which codes genes that are actively transcribed is associated with RNA polymerases while that DNA which codes inactive genes is more condensed and associated with structural proteins.

Modification of the structural proteins in chromatin alters the local chromatin structure, by methylation and acetylation.

As the cell prepares to divide, by entering mitosis or meiosis, the chromatin packages more tightly to facilitate segregation of the chromosomes during anaphase.

During anaphase stage of the cell cycle the individual chromosomes are visible by optical microscope.

Chromatin undergoes various structural changes during a cell cycle.

The DNA double helix in the cell nucleus is packaged by special proteins termed histones.

Histone proteins are the basic packer and arranger of chromatin.

The formed protein/DNA complex is called chromatin.

The basic structural unit of chromatin is the nucleosome.

The basic repeat element of chromatin is the nucleosome, interconnected by sections of linker DNA.

The nucleosomes bind DNA non-specifically, as required by their function in general DNA packaging.

Leave a Reply

Your email address will not be published. Required fields are marked *