DNA molecule is one of the major targets for UVR that can alter its molecular structure by forming different types of lesions leading to chronic mutagenic and even death of the cell. In comparison to UV-B, the wavelength of UV-A has poor efficiency in inducing the DNA damage; because they are not absorbed by native DNA. Before assessing the impact of UV-B radiation on DNA, we observed its effects on growth and survival of the test organism Scytonema sp. It was observed that growth and survival were severely affected by UV-B radiation for different durations. UV-B treatment causes loss in the cooperative binding property of DNA which is evident from the failure of complementary strands of DNA.