Practice question

Micrococcal nuclease from Staphylococcus aureus, calcium dependent endo-exonuclease, preferentially cleaves accessible linker DNA between nucleosomes due to steric exposure, showing mild sequence bias toward AT-rich regions. Limited digestion time course generates characteristic ladder pattern on agarose gel with fragments in multiples of nucleosome repeat length, enabling mapping of positioning and repeat determination. Core DNA tightly wrapped around octamer protected early, centromeric heterochromatin more resistant due to compaction, GC-rich naked DNA not preferentially digested. Assay remains gold standard for chromatin accessibility and nucleosome mapping in epigenetics studies.