Why Does Chromatin Look Like Beads on a String

Chromatin is a complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells. … Under the microscope in its extended form, chromatin looks like beads on a string. The beads are called nucleosomes. Each nucleosome is composed of DNA wrapped around eight proteins called histones.

Why does chromatin have a beads on a string appearance?

The primary protein components of chromatin are histones, which bind to DNA and function as “anchors” around which the strands are wound. In general, there are three levels of chromatin organization: DNA wraps around histone proteins, forming nucleosomes and the so-called beads on a string structure (euchromatin).

What are the beads on unfolded chromatin strings?

If this chromatin is subjected to treatments that cause it to unfold partially, it can be seen under the electron microscope as a series of “beads on a string” (Figure 4-23B). The string is DNA, and each bead is a “nucleosome core particle” that consists of DNA wound around a protein core formed from histones.