What are the functions of histones in chromosomes?

Histones are proteins that help organise and condense DNA into a compact, efficient form within chromosomes.

Histones play a crucial role in the structure and function of chromosomes. They are the main protein components of chromatin, the substance within a chromosome consisting of DNA and protein that forms when a cell divides. The primary function of histones is to package DNA into a smaller volume to fit within the cell. They achieve this by acting as spools around which the DNA winds, effectively condensing the DNA and allowing it to fit within the nucleus of a cell.

Histones are not just passive spools, however. They also play an active role in gene regulation. The winding of DNA around histones can control the accessibility of the DNA to transcription factors and other proteins that need to interact with the DNA. This means that histones can influence whether a gene is turned on or off. Modifications to histones, such as the addition or removal of chemical groups, can change the compactness of the DNA and thus its accessibility. This is a key mechanism of epigenetic regulation, where changes in gene expression occur without changes to the underlying DNA sequence.

Furthermore, histones are involved in DNA repair. When DNA is damaged, histones can help to recruit repair proteins to the site of damage. They can also change their shape to allow these repair proteins to access the DNA. This is crucial for maintaining the integrity of the genome and preventing mutations that could lead to diseases such as cancer.

In summary, histones are essential for the organisation and regulation of DNA within chromosomes. They condense DNA to fit within the cell, regulate gene expression through changes in DNA accessibility, and assist in DNA repair.