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Homologous Genetic Recombination in Xenopus: Mechanism and Implications for Gene Manipulation

Elsevier Science & Technology
DOI: 10.1016/s0079-6603(08)60361-x
  • Dsb
  • Gv
  • Ssa
  • Design


Publisher Summary This chapter describes the capabilities of oocytes and eggs from the South African clawed frog, Xenopus laevis, for causing the recombination of exogenous DNA molecules. The focus is on the mechanism of homology-dependent recombination as elucidated mostly through experimental results obtained in the laboratory. Recombination in oocytes proceeds by exonuclease resection and the annealing of complementary strands. The mechanism, which is usually called “single-strand annealing (SSA),” is nonconservative in the sense that two homologous parental sequences yield only one copy as a recombination product. Appropriately designed DNA substrates undergo very efficient homologous recombination after injection into the nuclei of Xenopus laevis oocytes. The requirements for this process are that the substrate should be linear, that it has direct repeats to support recombination, and that these repeats are at or very near the molecular ends. Taking advantage of direct nuclear injection, the large amounts of DNA processed in a single oocyte, and the accessibility of recombination intermediates, the mechanism of recombination is analyzed in detail in the chapter. The capability for SSA accumulates during the later phases of oogenesis and persists into the egg. This pattern suggests that, like many activities of full-grown oocytes, SSA is stored for use during embryogenesis.

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