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Dysgenic male recombination (MR) induced by the P strains T-007 and OKI rarely, if ever, occurs in the heterochromatin of chromosome two. One possible explanation is that the lack of heterochromatic exchange is due to the highly condensed chromatin in this region. Butyrate (a suspected modifier of chromatin structure) induced significant levels of heterochromatic MR in dysgenic hybrids derived from crosses involving two different P strains. This finding is consistent with the hypothesis that chromatin structure can influence the insertion and excision of P elements and hence MR. Analogous experiments were performed using third chromosome suppressor of variegation (Su(var)) mutations. Neither suppressor mutation induced any heterochromatic MR, suggesting that the mode of action of these Su(var) genes is different from, and more specific than, that of butyrate. One of the mutations (325) which is thought to influence meiotic recombination frequencies, causes some alterations in euchromatic MR in crosses involving the OKI strain. The other mutation, 318, affects neither meiotic nor dysgenic recombination. Su(var) 325 is the first known "factor" to influence meiotic and dysgenic recombination similarly. / Science, Faculty of / Zoology, Department of / Graduate

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Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 130-133).

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published_or_final_version / abstract / Biochemistry / Master / Master of Philosophy

Successful bacterial circular chromosome segregation requires that any dimeric chromosomes, which arise by crossing over during homologous recombination, are converted to monomers. Resolution of dimers to monomers requires the action of the XerCD site-specific recombinase at dif in the chromosome replication terminus region. This reaction requires the DNA translocase, FtsK(C), which activates dimer resolution by catalysing an ATP hydrolysis-dependent switch in the catalytic state of the nucleoprotein recombination complex. We show that a 62-amino-acid fragment of FtsK(C) interacts directly with the XerD C-terminus in order to stimulate the cleavage by XerD of BSN, a dif-DNA suicide substrate containing a nick in the 'bottom' strand. The resulting recombinase-DNA covalent complex can undergo strand exchange with intact duplex dif in the absence of ATP. FtsK(C)-mediated stimulation of BSN cleavage by XerD requires synaptic complex formation. Mutational impairment of the XerD-FtsK(C) interaction leads to reduction in the in vitro stimulation of BSN cleavage by XerD and a concomitant deficiency in the resolution of chromosomal dimers at dif in vivo, although other XerD functions are not affected.