Mass of human chromosomes measured for the first time

The mass of human chromosomes, which contain the instructions for life in nearly every cell of our bodies, has been measured with X-rays for the first time in a new study led by UCL researchers. For the study, published in Chromosome Research , researchers used a powerful X-ray beam at the UK's national synchrotron facility, Diamond Light Source, to determine the number of electrons in a spread of 46 chromosomes which they used to calculate mass. They found that the chromosomes were about 20 times heavier than the DNA they contained - a much larger mass than previously expected, suggesting there might be missing components yet to be discovered. As well as DNA, chromosomes consist of proteins that serve a variety of functions, from reading the DNA to regulating processes of cell division to tightly packaging two-metre strands of DNA into our cells. Senior author Professor Ian Robinson (London Centre for Nanotechnology at UCL) said: "Chromosomes have been investigated by scientists for 130 years but there are still parts of these complex structures that are poorly understood. "The mass of DNA we know from the Human Genome Project, but this is the first time we have been able to precisely measure the masses of chromosomes that include this DNA. "Our measurement suggests the 46 chromosomes in each of our cells weigh 242 picograms (trillionths of a gram).