February 26, 1951
Dear Gordon-
I just saw your small note in MCB, and wanted to ask you a bit more about it, as well as to find out how things have been going.
The new nutritional combinations were, I suppose, found in the background growth between prototrophs. Shouldn't it have been possible to minimize this difficulty by using sufficiently dilute inocula? But I suppose that you can make out an inverse argument even stronger than the one you presented: namely that certain combinations were found at sites where their selected (i.e. quasi-prototrophic) complements were not seen.
One point about these experiments suggested itself: I know that you do not recognize the "B-" factor in the stocks derived from 58-161 B-M-. Let us suppose that it is actually present, however, although masked by the M- mutation. Then, the absence of Biotin in the medium might prevent the development of some complementaries, if they carried B- now unmasked by recombination. This is not a very strong argument, but if we repeat experiments along these lines, we intend either to pretend that B- is still segregating or else use other stocks. Am I correct in thinking that your crosses involved BMP x TLB1?
One of my students, Phyllis Fried, is interested in this matter, and would like to carry out some experiments along the lines I already talked to you about, namely to determine whether, for example, M-T- and P-L- selections, isolated at random from appropriately supplemented plates, will show complementary segregation ratios for unselected markers such as B, B1, Lac, S, Mal, etc. Please let me know if you would rather we hold off on this program, that is, if you are planning anything similar. If you have any relevant data or suggestions as to the most fruitful stocks or lines of approach, we would be obliged to you for them.
You must now be in the last stages of your medical training. I don't suppose there's much point in asking you about your plans, what with Selective Service, but where are you interning? You must have heard about the topic of the Cole Spring Harbor Symposium this June (8-15)--is there any chance of seeing you there?
Sincerely,
Joshua Lederberg