Publication Date


Document Type


First Advisor

Griffiths, T. Daniel

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Cells--Effect of radiation on; DNA; Ultraviolet radiation--Physiological effect


There has been great debate concerning the roles of the pyrimidine(5-6)pyrimidine and pyrimidine(6- 4)pyrimidone lesions. Previous work in this area, with Chinese hamster ovary (CHO) cells, has shown the (6-4) lesion to be more important than the (5-6) lesion in affecting cell survival, DNA synthesis, mutation and sister chromatid exchange (SCE) induction. We used CHO cells AA8 (repair-proficient in removing both lesions), UV61 (removes only the (6-4) and not the (5-6) lesions) and UV5 (removes neither lesion). Cell survival studies showed UV5 cells were more sensitive to ultraviolet light (UV) than UV61 cells. DNA synthesis studies showed a fluence dependent effect. The (6-4) lesion played a greater role than the (5-6) in decreasing DNA synthesis at 2.5 J/m². At 5 and 10 J/m², the (5-6) lesion played a greater role in inhibiting DNA synthesis than seen at 2.5 J/m². DNA chain elongation was studied by using DNA fiber autoradiography. Our results indicated the (5-6) lesion did not form long-term blocks to DNA chain elongation. DNA fiber autoradiography was also used to detect and measure the activation of alternative sites of initiation. The (5-6) lesion did activate alternative sites. This activation remained longer than that seen in AA8 cells but was removed by 5 hrs. SCE studies showed the (6-4) lesion played a major role in SCE induction. Mutation results indicated the (5-6) lesion caused mutations more frequently than the (6-4), especially at fluences less than 1 J/m². The (6-4) lesion appears to play a greater role than the (5-6) lesion in cell survival, DNA synthesis, DNA replication (initiation and elongation) and SCE induction. The (6-4) lesion does play a role in mutation but the (5-6) lesion causes most of the increases seen in mutation frequency.


Includes bibliographical references (pages [105]-117)


v, 117 pages




Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type