Topic 17, homologous recombination.ppt.edu

Topic 17, homologous recombination.ppt.edu - Topic 17:...

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Topic 17: Homologous Recombination
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Learning objectives Be able to define the following terms: homologous sequences, DNA recombination, crossing over, genetic linkage, Holliday junction, DNA resolution Be able to list the molecular events required for homologous recombination (slide 11) Be able to list 3 ways in which DNA recombination can play a role in repairing DNA damage Be able to draw a diagram of a Holliday junction, and explain the 2 possible ways to resolve the junction Be able to explain the practical application of homologous recombination to manipulate complex genomes
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Terms to understand Homologous DNA sequences: 2 DNA molecules with very similar DNA sequences in the same order Need not be 100% match, but should be pretty close to 100% for efficient recombination rates DNA recombination: process of introducing new DNA sequences into existing DNA (often includes swapping sequences between 2 strands of dsDNA)
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Homologous recombination: the big picture Required for: Repairing dsDNA breaks Correct chromosome segregation in meiosis Also contributes to: Genetic diversity Process can be manipulated to generate recombinant organisms, especially useful for complex (large) genomes: can’t just cut and paste when millions of the same palindrome exist in the genome
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Terms to understand Crossing over: homologous (very similar) DNA sequences from different chromosomes line up next to each other and switch places Genetic linkage: a method to determine how close 2 genes are to each other based upon the frequency of crossing over together vs. crossing over separately
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How does this happen? Homologous recombination: the big picture
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Unlinked genes: they segregate independently Linked genes: they nearly always segregate together. They can segregate independently if crossing over takes place between them, but if they are very close to one another then likelihood of crossing over independently is very low
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Example of how linked genes can segregate independently: the closer they are to each other, the less likely this will occur
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Visualization of a crossing over event
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Topic 17, homologous recombination.ppt.edu - Topic 17:...

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