Date of Award

Spring 2004

Document Type

Restricted Thesis

Terms of Use

© 2004 Renuka R. Nayak. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts



First Advisor

Elizabeth Ann Vallen


Stem cells have the unique and defining ability to replenish short-lived cell populations, such as skin, intestinal lining and sperm. We examined the loss and replacement of germline stem cells in Drosophila melanogaster testes. Using a lacZ transgene, we marked a limited number of germline stem cells per testis and calculated the percentage of testes retaining a marked stem cell over time. From these analyses, we calculated the half-life of individual germline stem cells to be 13 days. However, counting the number of germline stem cells per stem cell niche over time revealed that the actual decline in the population of germline stem cells was significantly less than the predicted decline based on a half-life of 13 days. These results suggest that while germline stem cells are lost over time, the niche is repopulated to replace lost stem cells, thereby increasing the functional lifetime of the testis.