Epigenetics can be defined as persistent, heritable and reversible changes in gene expression without changes in the DNA sequence.
This is done mainly by Histone, nucleosome and DNA modification. The DNA is wrapped around histones to form a nucleosome and the nucleosomes (like beads on a string) form the chromatin. The chromatin (discussed in detail in the Epigenetics: Chromatin lesson) condenses to form loops which then lead to the formation of the chromosome. As we discussed in the cell cycle, the visible chromosome; also called the metaphase chromosome, will appear during the metaphase of the M phase of the cell cycle.