Article

Molecular and General Genetics MGG

, Volume 202, Issue 3, pp 394-402

Mitotic recombination between dispersed but related rRNA genes of Schizosaccharomyces pombe generates a reciprocal translocation

  • Philippe SzankasiAffiliated withInstitute of General Microbiology, University of Bern
  • , Christof GyslerAffiliated withInstitute of General Microbiology, University of Bern
  • , Ulrich ZehntnerAffiliated withInstitute of General Microbiology, University of Bern
  • , Urs LeupoldAffiliated withInstitute of General Microbiology, University of Bern
  • , Jürg KohliAffiliated withInstitute of General Microbiology, University of Bern
  • , Peter MunzAffiliated withInstitute of General Microbiology, University of Bern

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Summary

Recombination between dispersed yet related serine tRNA genes of Schizosaccharomyces pombe does occur during mitosis but it is approximately three orders of magnitude less frequent than in meiosis. Two mitotic events have been studied in detail. In the first, a sequence of at least 18 nucleotides has been transferred from the donor sup3 gene on the right arm of chromosome I to the related acceptor gene sup12 on the left arm of the same chromosome, thereby leading to the simultaneous change of 8 bp in the acceptor gene. This event must be explained in terms of recombination rather than mutation. It is assumed that it represents mitotic gene conversion, although it was not possible to demonstrate that the donor gene had emerged unchanged from the event. The second case reflects an interaction between sup9 on chromosome III and sup3 on chromosome I. Genetic and physical analysis allows this event to be described as mitotic gene conversion associated with crossingover. The result of this event is a reciprocal translocation. No further chromosomal aberrations were found among an additional 700 potential intergenic convertants tested. Thus intergenic conversion is much less frequently associated with crossingover than allelic conversion. However, the rare intergenic conversion events associated with crossingover provide a molecular mechanism for chromosomal rearrangements.

Key words

Mitotic recombination Schizosaccharomyces pombe