Background Information:

Chimera, an animal comprised of the head of a lion, the body of a goat, and the tail of a serpent, originated in Greek mythology.  However, this term means something different within the realm of medicine.  In relation to medicine and science, chimerism is two genetically distinct cell populations from different zygotes that reside within one zygote. A simpler definition to understand is two different sets of DNA in one individual.  This can occur through blood transfusions, transplantations, or during the development of an embryo.  Although scientists and researchers are unsure of the mechanism by which chimerism occurs, immense progress is being made in understanding this phenomenon. 

There are three main types of chimerism: tetragametic chimerism, microchimerism, and germ-line chimerism.  Tetragametic chimerism is defined by two or more different populations of genetically distinct cells that originated in different zygotes or the fusion of four gametes.  This type of chimerism is frequently congenital, and is believed to be fairly uncommon.  There are some physical characteristics associated with this type of chimerism such as blaschko’s lines, patches of hair growth on one side of the body and not on the other, and different eye colors.  Microchimerism is defined as a small number of cells that are genetically distinct from those of the host individual.  This is frequently observed in the exchange of maternal and fetal cells during pregnancy.  Fetal cells have been detected in a mother as late as two decades after birth of the child.  Lastly, germ-line chimerism is the physical mixing of cells from two different organisms (e.g. a sheep and a goat to produce a "geep"). 

This website will explore and explain the occurrence of chimerism in humans and animals, medicine, and society.