DNA provides a template for a cell to make the proteins it needs to survive. The survival of a cell is based on a number of different proteins that coordinate functions within a cell. These proteins, which include enzymes, do specialised jobs and control the acivities of the cell. Different cells have different activities, so whilst all calls contain the same DNA, different cells will only use certain segments of DNA.
Within a hair follicle, one of the segments of DNA utilised produces keratin, lots and lots of keratin. The keratin produced by the hair follicle makes long fiblres and continues to grow within the dermis (just under scalp level). This keratin emerges from your scalp as hair.
The repair of DNA is governed by a collection of processes that allows a cell to identify and repair damage to DNA.
Damage to DNA causes a change in the DNA sturcture and prevents normal replication. DNA methylation is a process by which methyl groups are added to DNA without any change to the DNA sequence. DNA methylation typically acts to repress DNA transcription. Repression of DNA transcription in the hair follicle leads to repressed keratin production.