Lecture 26 W11 - Lecture 26 (3-18-10) Notes I. Mapping the...

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Lecture 26 (3-18-10) Notes I. Mapping the gene responsible for Huntington’s disease HD) A. Disease is characterized by a progressive neurodegeneration 1. runs in families as an autosomal dominant trait B. Use of polymorphisms to localize the HD gene in humans 1. A polymorphism is a region of the genome where different individuals have different sequences. 2. One type of polymorphism is a restriction fragment length polymorphism (RFLP), which a sequence polymorphism creates or removes a site for a restriction enzyme 3. Researchers collected hundreds of RFLPs in a large family with HD. 4. They then painstakingly mapped the frequency of the RFLPs in the family. 5. The closer a RFLP maps to the HD, the better the correlation between the presence of a particular RFLP and HD. C. Linkage to a particular RFLP led to the identification of the gene that was altered in HD individuals 1. Individuals without symptoms have 11-25 copies of a CAG codon in the Huntington protein. 2. Affected individuals have over 40 CAG repeats, causing the protein to misfold and malfunction, leading to death of neurons in the brain. D. Now that the molecular basis of HD is known, PCR is routinely used to diagnose this
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Lecture 26 W11 - Lecture 26 (3-18-10) Notes I. Mapping the...

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