Researchers at the University of Edinburgh have used a human artificial chromosome to gain important knowledge about the functioning of the human cell cycle. Human artificial chromosomes were first created in 1997, and are part of a class named "˜microchromosomes', containing far less DNA than a regular human chromosome. Despite the name, they are not completely artificial, being made up partly of DNA extracted from human cells.The experiments were part of a joint project of the Wellcome Trust, the US National Institutes of Health and Nagoya University in Japan. They allowed us to improve our understanding of how chromosomes (the carriers of DNA) are distributed between two cells during cell division.Prior to cell division, the cell creates a copy of each chromosome. The two identical chromosome copies remain attached to each other by a structure called the centromere. The research helped to gain insight into the role of the centromere during cell division, and determine which factors can make it malfunction, creating cells with different numbers of chromosomes.The researchers hope that the knowledge gained will help them better understand chromosome-related diseases such as Down's syndrome, and certain kinds of cancers.