What Is Chromatin?: This is an illustration of a chromatin fiber unraveling progressively. It unravels to reveal nucleosomes (8 histones with DNA wrapped round them) and the various bases in the DNA molecule.
'In leukemia cells it is often the case that genes are reactivated that, in physiological terms, mediate the self-renewal of blood stem cells. In a common subtype of acute myeloid leukemia, this abnormal activation of such self-renewing genes is apparently caused by structural modifications of the DNA packaging. A targeted drug-based inactivation of the two chromatin regulators will interrupt the self-renewing program, thereby causing leukemia cells to revert to normal blood cells.'
A nucleosome is the basic repeating unit of eukaryotic chromatin. In a human cell, about six feet of DNA must be packaged into a nucleus with a diameter less than a human hair. A single nucleosome consists of about 150 base pairs of DNA sequence wrapped around a core of histone proteins. The nucleosomes are arranged like beads on a string. They are repeatedly folded in on themselves to form a chromosome.