Introduced in the 1960's, CHO cells have twin female X chromosomes and a nutritional need for the amino acid proline. With this knowledge, researchers are able to manipulate the cells in genetic and developmental experiments. Cancer studies using CHO involve inducing mutations, describing cellular processes, and examining the curative effects of potential treatments. Most recently, hamster cells were used in the human genome project since they have the ability to hold on to pieces of human DNA. This aids the mapping of the human genome by allowing the creation of scorecards for each DNA fragment (or genetic marker) inserted.