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 at dogwood.botany.uga.edu
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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