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Archived Comments for: DNA transposons and the role of recombination in mutation accumulation in Daphnia pulex

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  1. NHEJ Vs homologous recombination

    Ronald Chalmers, Nottingham University

    28 February 2011

    Quoting from the intro:

    "Although, DNA transposons are generally not thought to exhibit replicative gains when mobilized, for members of subclass 1, copy number can increase due to homologue-dependent DNA repair after excision at homozygous loci, which can result in the reconstitution of a TE in the donor location and, therefore, replicative gain."

    My understanding is slightly different from this. Class 2 DNA transposons become amplified by two mechanisms operating during S phase of the cell cycle. Following excision, the empty donor site is restored to a filled donor site by homologous recombination with the sister chromosome (ie. the product of replication). Furthermore, if the transposon excises behind one replication fork and inserts in front of another fork, it makes further copy number gains.

    In some organisms the repair of double strand breaks by homologous recombination is restricted to S phase. During the rest of the cell cycle non homologous end joining predominates. There is therefore very little scope for replicative gains by homologous repair from the homolog. I do not know if this is true in daphnia, but it probably is.

    English and Jones 1995 did some nice work in this area with the Ac/Ds system in maize.

    Competing interests