Abstract
Repeat-induced point mutation (RIP) is a hypermutational process that alters duplicated DNA sequences in Neurospora crassa. In previous studies, five of six large (>100 kb) chromosome segment duplications (Dp’s) examined were shown to dominantly suppress RIP in smaller (<5 kb) duplications. The suppressor duplications were >270 kb, whereas the lone non-suppressor duplication was ∼117 kb. We have now screened another 33 duplications and found 29 more suppressors and four more non-suppressors. All 22 suppressor duplications whose size could be estimated were >270 kb, whereas two newly identified non-suppressor duplications examined were 140–154 kb. RIP was suppressed in a subset of crosses heterozygous for more than one ordinarily non-suppressor duplication. These results strengthen the hypothesis that large duplications titrate out the RIP machinery and suggest the “equivalence point” for the titration is close to 300 kb.
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Acknowledgements
Mukund Ramakrishnan provided assistance in some of the experiments. We thank Bob Metzenberg for sending us strains. Charges for strains obtained from the Fungal Genetics Stock Center (FGSC) were generously waived. The FGSC is supported by National Science Foundation grant BIR-9222772. PKS was supported by a Research Fellowship from the CSIR-UGC.
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This article is dedicated to the memory of Robert L. Metzenberg.
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Singh, P.K., Kasbekar, D.P. Titration of repeat-induced point mutation (RIP) by chromosome segment duplications in Neurospora crassa . Genetica 134, 267–275 (2008). https://doi.org/10.1007/s10709-007-9234-6
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DOI: https://doi.org/10.1007/s10709-007-9234-6