Practice question

Nucleosome repeat length encompasses DNA protected in core plus intervening linker. Micrococcal nuclease partial digestion of human chromatin followed by agarose gel electrophoresis shows regular ladder with approximately 200 base pair increment. Core particle contributes 147 base pairs wrapped around octamer, linker adds 20 to 60 base pairs varying by cell type, average about 53 base pairs in humans, giving total near 200 base pairs. This spacing dictates H1 binding stoichiometry and ability to fold into 30 nanometer fiber. Shorter repeats occur in yeast about 165 base pairs, longer in cortical neurons.