BIO
3 DNA Replication, Repair and Recombination

3 DNA Replication, Repair and Recombination - Essential...

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Chapter 6 DNA Replication, Repair, and  Recombination Essential Cell Biology Fourth Edition
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Genetics The science of heredity Deals with the study of how genes control the characteristics of a proband and how those heritable traits are transmitted and vary in expression from parents to offspring The children within this family resemble each other more closely than they do either of their parents, since they share a greater number of common genes with each other, versus with any one parent alone. They all also share elements with both the cat and the chicken too!
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DNA Replication Defined as the duplication process required of living  cells  for survival and regeneration Must precede cell division to produce 2 daughter  cells Required for cell maintenance and continuous  surveillance of the hereditary material Required for cellular repair due to environmental &  chemical damage (radiation, free radicals, etc.)
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Cell Cycle
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Base-Pairing Enables DNA Replication New DNA is always synthesized in the 5’  3’ direction
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DNA Synthesis Begins at Replication Origins DNA is the template/mold for it’s own replication. S & complementary S’ strands serve as a template to guide the sequence of a new strand. 
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Nature of DNA Replication? Watson and Crick in 1952 published their famous 2 page paper  which elegantly described the structure of the DNA double helix. They suggested a copying mechanism for DNA  at the conclusion of their first paper.  In a second follow-up paper they suggested the mechanism of replication is  Semi-Conservative   such that each DNA strand serves as a template for the new daughter strand. This met with opposition and the suggestion of a second mechanism  called  Dispersive Replication  which did not involve DNA unwinding  by Max Delbruck . A third camp believed DNA replication was  Conservative , with the parent helix remaining in tact after copying with the new helix  composed of two completely new strands.
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Meselson –Stahl Experiment
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Considered one of the most  elegant experiments ever  performed. To rule btwn last results,  M & S heated the resulting DNA and then centrifuged The resulting 1X DNA. Result was distinct band of 1 Hv and 1 Lt DNA chain,   not a mixed Hv & Lt or  intermediate mottled DNA chain density .
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Parent DNA Double Helix Parent DNA Double Helix Daughter DNA  Daughter DNA  Double Helices Double Helices DNA Replication DNA Replication is Semiconservative is Semiconservative
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DNA Polymerization DNA is made in the          5’   3’ direction,  with  release 2  phosphates.
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DNA Double Helix Opened at Replication Origins Bacteria with a circular  genome have typically
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