July 29, 1946.

Dear Mrs Lindegren:
Enclosed you will find a loose draft of a note on the mutant detection

method
3 Some of the wording has to be changed, but I think it is well

enough described to refresh your recollection of it as I spoke to you
about it at Cold Spring Habour. I hope it my also serve to recall to
you that you promised to send me 3 and alpha strains of yeast that could
be used for studjing biochanical mutants. I would appreciate them very
mich, It would be to your own advantage to mam send a strain that will
hybridize with forms whose fermentation pattern is interesting to you,
80 that when I send you back some mutants (as I promise to) you can breed
them into your stocks, and use them as markers. If you do send them out,
I would appreciate any information you may have on their vitamin recuire—
ments already existing,

With best regards,

Sincerely yours,

Joshua Lederberg,