Mutagenesis suggestions

Russell Malmberg russell at DOGWOOD.BOTANY.UGA.EDU
Thu Aug 15 13:06:00 EST 1991

1.  With regard to mutagen dose vs. seed survival:  37% survival

  Simple theoretical models of mutagenesis predict that the maximum
  yield of mutants, when considering the combination of mutagenicity
  and lethality, will occur at 37% survival.  (see appendix)
  This of course ignores the problems of multiple mutants per individual,
  but everyone backcrosses mutants 5 or 6 or 7 times anyway.

  In practice I usually use try various mutagen doses until I get 
  40 to 50 % survival.

2.  Lot size of M1 pools -- a suggestion some may find useful

  A possible balance point between pooling all the M2 seeds into one
  large pool, versus collecting seeds from each M1 plant individually:
  Project the size of your M1, then take the square root.
  Pool the seeds from this many plants together in a single M1 pool.

     Russell Malmberg
     russell at

Appendix for the theoretically inclined:

     M = total number of mutants
     N = total number of individuals
     l = fraction alive after mutagenesis
     m = fraction mutant among those alive
     d = dose of mutagen

  assume l = e ** (-k1 d)  which is exponential survival
  assume m = k2 d which is linear dose response

     M = mlN
     M = k2 d  e** (-k1 d)

  if you now take dM/dd = 0, and solve for d
  the maximum mutant yield will occur at d = e**-1 = 37%

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