Evolution’s Speed – What Kinds of Mutations Are There?

Collage of x-men

This is part of a series: How Fast is Evolution?
Previous: Evolution’s Speed – My Assumptions and First Guesses
Next: Evolution’s Speed – How Common Are Substitution Point Mutations?

I might have figured out how to test in a lab for irreducible complexity the practical limit of evolution.  One of the main arguments of the Intelligent Design movement is that many parts of living things are too complicated to appear by evolution.  Intuitively, this makes sense, and I ran into evolution’s practical limit even in self-copying computer programs.  But how can someone test for irreducible complexity in a lab?

One way is to try Michael Behe’s knockout test – systematically try knocking out every piece of a machine, and see if there are any parts that aren’t absolutely essential.  If everything’s critical, the system clearly couldn’t appear by evolution, because there simply is no previous step.  Either the whole thing appeared fully formed, or it wouldn’t have appeared at all.  I have a different idea: push evolution fast enough that you can see it happen, and watch for it to hit a wall.

I laid out the details here, and now I want to find out if this experiment would be practical – I might need an impractically huge population of bacteria to make it work.  The first thing I need to learn is all the types of mutations that happen to living things:

  • Add a random letter to a random place
    These are called insertion mutations
    Note that sometimes thousands of random letters appear in a single stretch, not just one
  • Remove a random letter
    These are called deletion mutations
    Like insertion mutations, thousands can disappear in a single chunk
  • indel mutations
    A combination of overlapping insertion and deletion mutations, in which it’s not clear afterward exactly which changes were caused by insertions and which by deletions
  • Change a random letter
    These are called substitution mutations
  • Copy a random chunk
    These are called duplication mutations
  • Delete a random chunk
    These are also called deletion mutations
  • Move a random chunk
    These can be called DNA slippage, strand slippage, or replication slippage.  They usually come with side effects, since they usually won’t stick to the new part of the genome that they’re in.  It might help to imagine copying two cassette tapes by touching the old tape to the new (just assume that this would actually work).  If either tape pinches while copying, you get strand slippage.  The difference with DNA is that the data on one strand has to be a mirror image of the other, or else it won’t stick very well.
  • Flip a random chunk
    These are called inversions

This is part of a series: How Fast is Evolution?
Previous: Evolution’s Speed – My Assumptions and First Guesses
Next: Evolution’s Speed – How Common Are Substitution Point Mutations?

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