ps_8_answers - Bio 115 Problem set #8 March 11, 2005 1. You...

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Problem set #8 March 11, 2005 1. You are studying Slater syndrome, which is associated with a progressive loss of balance, social withdrawal and shyness. Using genetic techniques, you determine that the Slater syndrome disease gene lies within a 4 megabase region of chromosome 4. You obtain a series of cosmids with overlapping inserts that cover this region. a. What term describes a series of genomic DNA clones with overlapping inserts? contig b. The computer programs available for predicting genes are sometimes unreliable. Thus, you decide to directly identify expressed genes from this 4 Mb region. How can you do this? 2 points Best- Use the cosmid inserts to probe cDNA libraries. Acceptable- Clone cosmid inserts into exon trapping vectors and identify exons by exon trapping. c. You isolate and sequence the disease gene from normal people and also from individuals affected by Slater syndrome. The gene’s structure is shown below. In individuals with the disease, exon 2 is always missing. You also notice that several transposons occur in the introns of this gene. What is the most likely mechanism by which this exon is lost? 2 points Exon: 1 2 3 Transposon: 1 2 Recombination between transposon 1 and 2 resulting in loss of the intervening DNA. Exon: 1 3 Transposon: 1/2 recombinant d. The 5’ UTR of the Slater syndrome gene is unusually long and the AUG occurs in a poor translational context. Surprisingly, the gene is translated at a high level. Furthermore, when cells are infected with a picornavirus, the gene is translated at a high rate. Provide the most reasonable explanation for these observations. This gene must have an IRES that allows cap-independent translation. 2. What are linked and dispersed gene families? 3. How does breaking up genes by insertion of introns facilitate the evolution of proteins with novel properties? When parts of genes (exons) are shuffled to new places by non-homologous recombination or chromosomal rearrangements, the breaks don’t have to occur at precise sites, nor does the insertion. Almost anywhere in an intron will work. - 1 -
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ps_8_answers - Bio 115 Problem set #8 March 11, 2005 1. You...

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