RADIATION - RADIATION 1..,butinlesser .Asionsareformed,...

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RADIATION      1. X rays and gamma rays ionize atoms and molecules. This can be fatal to cells, but in lesser  doses these forms of radiation act as mutagens. As ions are formed, they can combine with bases  in DNA, causing errors in DNA replication and repair. In some cases, chromosomes may even  break apart.       2. Ultraviolet light acts in a different way. Exposure may result in the formation of thymine  dimers, which can cause serious damage to DNA. DNA affected this way cannot be transcribed  or replicated. If not repaired, this type of damage leads to most cases of skin cancer.           Damage of this type can sometimes be repaired by enzymes. Light-repair enzymes use visible  light energy to separate the thymine dimers back to the original form. Excision repair cuts out the  damaged section of DNA and fills the gap with a new section of DNA complementary to the 
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