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The Joshua Lederberg Papers

Letter from Francois Jacob to Joshua and Esther Lederberg pdf (257,045 Bytes) transcript of pdf
Letter from Francois Jacob to Joshua and Esther Lederberg
Item is handwritten. Item is a photocopy.
Number of Image Pages:
4 (257,045 Bytes)
1955-07-31 (July 31, 1955)
Jacob, Francois
Lederberg, Esther
Lederberg, Joshua
Reproduced with permission of Francois Jacob.
Lederberg Grouping: Correspondence C
Box Number: 11
Folder Number: 88
Unique Identifier:
Accession Number:
Document Type:
Letters (correspondence)
Physical Condition:
Series: Correspondence, 1935-2002
SubSeries: 1953-1960
Folder: Jacob, Francois
July 31
Dear Esther and Josh
I apologize in answering so late your letter of July 16 but I was in Britanny[SIC] for holidays and I just got your letter. Incidentally I did not receive any letter from Esther last year and I suspect it to have arrived during a post strike in which a good deal of the mail was lost.
I am very happy to have your criticism on our work although I can hardly agree with some of them. Until now we have only worked with Hfs[?] strains and only with the TlAgTIlacfale[?] prophage segment All the results we have now create a coherent picture for this segment (and the OF+ segment of the F+). It seems quite clear, from the data of "erotic reduction" we have obtained with several inducible prophages, that, is a cross H fly+ x F-ly-, practically each time the inducible prophage enters the F-, it develops. It appears unambiguous therefore that only a segment of the Hf enters the F- with high frequency.
Its[SIC] not know, for the time being, how to reconcile these results with your data from the het segregation.
I would just like to make a few remarks. The first one is that our data deal only with the Th-lambda segment of the Hf - The mechanism we have assumed, Elie and I, in our last short paper is only concerned with such data and we have no hypothesis now to account for the "normal frequency" cases where markers of the Sz-M sugar[?] refrois[?] are transferred. My second remark is that little is know[SIC], for the time being, on the true nature of the strains. It appears from Lennox's and my own experiments on transduction in k12 that transduced strains are obtained carrying two allels[SIC] of given maiter[?], and which segregate "haploids" clones for more than 100 generations. What is the relation between the het obtained through crosses and such transduced strains, and even with double lysogenic strains carrying two lambda prophage (which are obtained by superinfection[?] , transduction and recombination), we do not know. It seems to me that a good understanding of all these cases of partial diploidy is necessary. We have not (Elie and I) tried to work the Het strain
you sent to Jacques but Jacques has tried to do some experiments with it, without any success I believe.
To answer some of your remarks, we assume a single histage[?] group[?] OTL AgT Las falg lambda and our theory explains very easily the different falg segregation ratios in Hp ly+ x F-ly- and other crosses. Each time, lambda[?] comes into the F-, the prophage develops and the zygote is destroyed (50 to 60 % of the conjugation). Only when a breakage occurs between O and lambda, the prophage does not come in the F- and the zygote is viable. Twice falg[?] and lambda are closely limited, such breakage occurs generally before, fale and only the zygote in which a TL or TLAy or TLAgTILac segment has entered can give a recombinant - the falg frequency in these decreased by a 10 times factor with lambda.
Of course, our proposed scheme is only a tentative one and the earlier it is reflected by new data, the better it will be. This is by definition our job. The most
efficient way for this is to keep in close contact and we would appreciate very much to get your MS (thank you for the 3 short notes you sent me some weeks ago).
I thank you very much for your kind offer for me to come an work with you during some months. I appreciate greatly your invitation. Unfortunately, I am now the father of four children ranging from 6 to 1 year, and I am terrified by the thought of carrying such a squadron overseas. I hope to have one day a new opportunity of going to the states for some weeks and I would very much like to spend some time and talk with you. I keep an excellent "souvenir" of the too few hours I had in Madison with you. May I ask whether you will not come soon in Europe. Every-body here would greatly appreciate your visit.
Many thanks again and I hope a new theory will soon emerge from K12 data.
Yours sincerely
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