Each human cell, at metaphase, normally contains 23 pairs of chromosomes, or 46 in total. Within these are four copies of 3.5 billion base pairs of DNA. In a new study, a team of scientists from the United Kingdom and the United States used a method called phase-sensitive X-ray ptychography to determine the number of electrons in a spread of all 46 human chromosomes; they found that the chromosomes were about 20 times heavier than the DNA they contained...
