BIOL 039 Lecture Notes - Lecture 19: Pyrimidine Dimer, Bruce Ames, Ionizing Radiation
Document Summary
Ionizing radiation (ir) from x-rays or radioactive materials causes damage in multiple ways the most serious are single-stranded or double-stranded breaks in dna. As a result, ir can cause structural changes in chromosomes such as deletions, duplications, inversions, and translocations. Hermann j. muller and edgar alternburg measured the frequency of x-linked recessive lethal mutations in drosophila. The clb-test, where clb is the name of the balancer x-chromosome. Muller demonstrated that exposing drosophila sperm to x-rays increased the mutation frequency. In 1946, muller received the nobel prize in physiology or medicine for this important discovery. Non-ionizing radiation from the uv light alters dna by inciting the formation of aberrant structures called photoproducts, e. g. pyrimidine dimers. Pyrimidine dimers are produced by the formation of one or two additional covalent bonds between adjacent pyrimidine nucleotides. One common photoproduct is a thymine dimer, formed between the 5 and. Thymidine dimers block dna replication and activate error-prone dna.
