Practice question

Standard ChIP workflow includes formaldehyde crosslinking, chromatin shearing to 200-600 base pairs, immunoprecipitation with specific antibody and stringent washes to remove non-specific chromatin. To recover DNA for downstream analysis, protein-DNA crosslinks must be reversed by incubation at sixty-five degrees Celsius with high salt, followed by RNase A and proteinase K digestion to remove RNA and protein. Purified DNA is then isolated using phenol-chloroform or spin columns, yielding clean template for PCR, qPCR or sequencing. Reversal and purification constitute final steps before DNA analysis.