In domestic animals, some markers such as GDNF family receptor alpha-1 (GFRα-1), Promyelocytic leukaemia zinc finger (PLZF) [15], Thy-1 Membrane Glycoprotein (THY1), and Ubiquitin C-terminal hydrolase 1 (UCHL1) [16] have been used to enrich and identify the undifferentiated spermatogonia. The gene discussed is THY1; the disease is leukemia.