03基因突变eng v整理.ppt

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03基因突变eng v整理

03 基因突变 Gene Mutation Gene Mutation Change in genes caused by change in structure of the DNA. Base(s) in DNA is (are) changed to other(s), or a base(s) is (are) added or removed. Rearrangements of the chromosomes occur and are also considered. Mutations are heritable changes in genetic material. 1. Mutagens or Mutagenic Agents These are substances, conditions and forms that significantly increase the frequency of mutations. Mutations can occur at a spontaneous rate, or a far greater rate when there is exposure to mutagenic agents. Exposure to too high a level of mutagens can threaten the survival of a species; e.g., frog species in the states of Washington and Oregon are facing extinction. This appears to be caused by reduced atmospheric ozone, and the resulting increased level of ultraviolet radiation. A forms of energy Examples of a forms of energy are ultraviolet light, x-rays, cosmic energy, gamma radiation, alpha particles, beta particles and neutrons. Ultraviolet (UV) light UV light has shorter wavelengths than visible light. Though these waves are invisible to the human eye, some insects, like bumblebees, can see them! Scientists have divided the ultraviolet part of the spectrum into three regions: the near ultraviolet, the far ultraviolet, and the extreme ultraviolet. The three regions are distinguished by how energetic the ultraviolet radiation is, and by the wavelength of the ultraviolet light, which is related to energy. The near ultraviolet, abbreviated NUV, is the light closest to optical or visible light. The extreme ultraviolet, abbreviated EUV, is the ultraviolet light closest to X-rays, and is the most energetic of the three types. The far ultraviolet, abbreviated FUV, lies between the near and extreme ultraviolet regions. It is the least explored of the three regions. Ultraviolet Radiation causes pyrimidine dimers. These can block DNA repl

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