Each time a human cell divides, it must first make a copy of its 46 chromosomes to serve as an instruction manual for the new cell. Normally, this process goes off without a hitch. But from time to time, the information isn’t copied and collated properly, leaving gaps or breaks that the cell has to carefully combine back together.
Researchers have long recognized that some regions of the chromosome,called “fragile sites,” are more prone to breakage and can be a breeding ground for human cancers. But they have struggled to understand why these weak spots in the genetic code occur in the first place.
A comprehensive mapping of the fragile sites in yeast by a team of Duke researchers shows that fragile sites appear in specific areas of the genome where the DNA-copying machinery is slowed or stalled, either by certain sequences of DNA or by structural elements. The study, which appears May 5 in Proceedings of the National Academy of Sciences, could give insight into the origins of many of the genetic abnormalities seen in solid tumors. More here Where DNA’s copy machine pauses, cancer could be next.