What is chromatin immunoprecipitation?

Chromatin immunoprecipitation is a technique used to see if certain proteins interact with any DNA sequences (along with figuring out which ones). The process is started by attaching a protein to a DNA molecule. Once this is done, the DNA is cut up into shreds about ~500 bps long. This will create a solution of free DNA and DNA that is attached to the introduced protein. The solution is then treated with antibodies that bind to the introduced protein. This will make the proteins (and their associated DNA fragment) clump up into a dense complex, which when centrifuged will separate from the rest of the DNA fragments. The complex can then be extracted, treated with salt (to separate the DNA and protein), then put through PCR to amplify the strand. This way scientist can see which fragment was interacting with the protein.