Lecture_8_2011_sep19 - Introduction to Biophysics Lecture 7...

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Introduction to Biophysics Lecture 7 DNA
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DNA can be damaged by mutagens, which change the DNA sequence. Oxidizing agents, alkylating agents High-energy electromagnetic radiation: UV, X-ray For example, UV light can damage DNA by producing thymine dimers oxidants such as free radicals or hydrogen peroxide produce base modifications and double-strand breaks. The most dangerous are double-strand breaks, as these are difficult to repair. Many mutagens fit into the space between two adjacent base pairs - aromatic and planar molecules. This inhibits both transcription and DNA replication, causing toxicity and mutations. As a result, DNA intercalators are often carcinogens . Nevertheless, due to their ability to inhibit DNA transcription and replication, these toxins are also used in chemotherapy to inhibit rapidly-growing cancer cells. DNA damage
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Heavy exposure of your skin to UV light causes many such thymine crosslinks to form in the DNA. Fortunately, we have repair enzymes that can remove the thymine crosslinks and restore the DNA in your skin cells back to the correct sequence. When you get a sunburn, it is because you have caused more thymine crosslinks than can be repaired, so the cells generally just die. This results in the pain and dead skin you get with sunburns.
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A DNA helix usually does not interact with other segments of DNA, and in human cells the different chromosomes even occupy separate areas in the nucleus called "chromosome territories". Chromosomal crossover two DNA helices break, swap a section and then rejoin. increases the efficiency of natural selection and can be important in the rapid evolution of new proteins
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DNA Replication DNA replication. The double helix is unwound by a helicase and topoisomerase . Next, one DNA polymerase produces the leading strand copy. Another DNA polymerase binds to the lagging strand . This enzyme makes discontinuous segments before DNA ligase joins them together.
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Where we can find DNA? in nuclei, plasmids, mitochondria, and chloroplasts
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can be transformed into organisms in the form of plasmids or in the appropriate format, by using a viral vector . The genetically modified organisms produced can be used to produce products such as recombinant proteins , used in medical research, or be grown in
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This note was uploaded on 12/09/2011 for the course PHYS 570 taught by Professor Staff during the Fall '08 term at Purdue University-West Lafayette.

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Lecture_8_2011_sep19 - Introduction to Biophysics Lecture 7...

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