In future, if the clock can be shown to be reliable across various tissue types, we suggest the STR clock will also be relevant for counting cell divisions that have happened in a normal process such as haemopoiesis, or in abnormal processes such as leukaemia, and cancers in general, to estimate the age of that medical condition or tumour, as advocated by Wasserstrom et al. [9]. The gene discussed is CLOCK; the disease is leukemia.