http://link.springer.com/referenceworkentry/10.1007978-3-642-16483-5_2262 Day 66 has 20 protein-coding genes (browser view). Inside one of those genes, FHIT, lies FRA3B, a fragile site. FRA3B is the most common place for DNA to physically break from exposure to genotoxic chemicals like those in cigarette smoke, and is frequently found broken in cancer.
Click here to see the sequence of Day 66 with FRA3B underlined.