466 Chapter 14 • Mutation, Repair, and Recombination of the deletions are of repeated sequences. Figure 14-23 shows 9 deletions analyzed at the DNA sequence level in the lacI gene of E. coli . The results of further studies have shown that the longer repeats constitute hot spots for deletions. Duplications of DNA segments have also been observed in many organisms. Like deletions, they often occur at sequence repeats. It must be noted that, in addition to their origin by replication slippage, deletions and duplications could be generated by offset homologous recombination between copies of the repeats. Point Mutations Deletions Amino acid number FS5, FS25, FS45, FS65 FS2, FS84 S114 S58 A6 S28 25 50 75 100 125 150 175 200 225 250 275 300 325 LacI gene 350 S42 S56 S24 S86 S10 S136 S120 S32 S65 S23 S74 S112 Figure 14-22 The distribution of 140 spontaneous mutations in lacI. Boxes indicate position of point mutations, with red designating fast-reverting mutants. Deletions are represented in gold. Circles designate larger deletion and insertion mutants. Allele numbers correspond
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