This combination of DNA and specialized proteins creates a dense, compact fiber called chromatin. To probe the structure of chromatin, Rydberg used ionizing particles from the cyclotron to create fragments of chromatin. As predicted four years ago by Life Sciences Deputy Head Aloke Chatterjee and his colleague William Holley, the size distribution of the chromatin fragments provides a signature of the structure. Amy Kronenberg's group has determined that very large deletions and chromosomal translocations can be caused by energetic protons and nitrogen ions. Using a series of different cells with different chromosomal targets for mutation, they showed that the number of mutations detected was highly dependent on the location of essential genes on a particular chromosome.
Ongoing experiments seek to measure the frequency of whole chromosome loss using new model systems.
The loss of whole chromosomes can be a major factor involved in both birth defects and cancer. This research effort is part of the NASA Specialized Center of Research and Training that involves LSD's Department of Radiation Biology and DNA Repair and the Department of Radiological Health Sciences at Colorado State University. Kronenberg's group is also investigating the role of programmed cell death and DNA repair in susceptibility to mutation. LSD's Priscilla Cooper is directing a research effort in which the cyclotron is used to produce alpha particles that simulate those emitted by radon. Radon, a radioactive gas, is the dominant source of natural background radiation.