Re: Muller's Ratchet

From: Scott Chase (
Date: Fri 20 Jun 2003 - 17:24:37 GMT

  • Next message: Chris Taylor: "Re: Precision of replication"

    >From: "Wade T. Smith" <>
    >To: Memetics Listserv <>
    >Subject: Muller's Ratchet
    >Date: Fri, 20 Jun 2003 07:58:31 -0400
    >Here is a fine tool, mentioned in a forward I supplied to the list the
    >other day, which would seem to remove all unsightly replicators achieving
    >100% fidelity with celerity....
    >Muller's Ratchet, the name that geneticists give to the grim process of
    >irreversible genetic decay that affects asexual organisms and
    >nonrecombining genome parts (like the Y chromosome).
    If there were 100% fidelity in replication (ie- no mutation) how could there be a genetic decay and a need to invoke Muller's ratchet? My understanding is that Muller's ratchet applies to cases where deleterious mutations will accumulate in an asexual population, mutations which cannot be purged via sexual recombination and which may overcome the original alleles due to the originals being lost to drift.

    OTOH 100% accurate replication would mean that there would be no variation. Variation is the motor for evolution. A population of clones giving rise to clones will have no changes in allelic frequencies. Since adaptive landcapes can change over time, the trait that may be beneficial today may give no help or may hurt tomorrow. A population without variation will not track the changes in environment.

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