The term has multiple uses in modern biology. One prominent definition is an animal that has multiple different populations of genetically distinct cells that originated from different zygotes. Some humans are naturally chimeric, sharing cells from a twin (often one that was never born) or a parent.<ref>http://www.theage.com.au/cgi-bin/common/popupPrintArticle.pl?path=/articles/2003/11/27/1069825920727.html </ref>. | The term has multiple uses in modern biology. One prominent definition is an animal that has multiple different populations of genetically distinct cells that originated from different zygotes. Some humans are naturally chimeric, sharing cells from a twin (often one that was never born) or a parent.<ref>http://www.theage.com.au/cgi-bin/common/popupPrintArticle.pl?path=/articles/2003/11/27/1069825920727.html </ref>. |