UNIVERSITY OF LONDON POSTGRADUATE MEDICAL SCHOOL OF LONDON . Telegrams POSGRADMED CHISK LONDON . DUCANE ROAD Telephone Department of Bacteriology. LONDON, W.12 SHEpherds Bush 1260 (4 linas) 4 August,1954. Dear Joshua, I am writing to ask you whether you can let me have some more detailed information about the products of segregation of your micromanipulated zygotes. What I would like to know,in particular is whether you have isolated 1) any recombinant from those zygotes ’ which also segregated the Hfr parental type; 2) any reciprocal recombinants from a single zygote. My main reason for wanting this information is as a basis to formulating a plan of work from ep tember on. Since my return fmm the U.S. I have done no experimental work at all,due to unforseen shortages of staff. As from the end of this month I shall have plenty of time once again,and also a good Ph.D. student to play with and I would like to pick up the threads in their present position, I do'nt know whether you have yet heard of the recent experiments of Wollman & Jacob,using my Hfr strain,which will . Shortly be appearing in the Comptes Rendus. They have found that when Hfr(A) & F-(o) are aerated in broth for a short time and then plated on a sensitive strain, free A having being removed by washing & ) treatment with antiserum and the Hfr parent rendered inactive with .'Streptomycin,one infectious centre is found for about every two Hfr parental celle initially present. Since the F-(o) strain was also f/Aosthis means that A-prophage is transferred to the "zygote" with “a very high(if not 100%)frequency and. then undergoes spontaneous (erotic! )induction. Moreover,l) in the cross, Hfr(A) x. F-(A~defective), -prophage is transferred to about 50%:0f the progeny;2)in the cross Her(o) x F-(o),the Hfr Gal, marker is found in a high proportion of recombinants. Incidentally,they have confirmed my finding that,with this Hfr strain,those markers which do not lie on the (TL)-Lac linkage group are not inherited with high frequency. They postulate that A& Gal4 actually lie here but distal to Lac + i.e.obviously linked to (TL). They also suggest that spontaneous inductions of this kind may account for the eliminations but this does not seem to make sense ‘to me. I am not yet happy,though longing ta be convinced,about the Question of partial or complete zygotes.. Could your isolations of the Hfr parent from single "zygotes" not be explained by the frequent formation of unstable heterokaryons, between the complete nuclei of: Which partial "true" zygotes were sometimes formed? Hence my query :@8 to whether you had isolated Hfr parental + recombinant from the same "zygote" cell. From Rowley's work(shortly coming out in the DECENT) I now think there is good evidence for only one chromosome. a eee ee a o «4 I feel another year should see the genetical part of the x-12 proctlem well on the way to solution. I am rather tired of it. Approaches to the problems associated with tre nature of "F" are difficult to visualise,but,Il feel,this problem is of more funda venta] importance than thegenetics per se. We have had virtually no summer weather at all this @ year. JI hope you are bearing up in the hot weather at Madison. Or have you gone to Wood's Hole or some other pleasant spot? I am hoping that I may see luca Cavalli on his way to visit you. My best wishes to Esther and yourself. I hope we meet again sometime under more leisurely coniitions. Are you never coming to Europe? Yours, €——- First fold here ~——> é & y = 8 BW Le Q. yp > ce rob Ba > Ze o 9 : j i a my Pas c oo) ow Bm SS ued wy < | bt ® # © SE <6 B ok eH ¢ eB onn S Bee £ £ o 2 = “pgs n 9 , + “AQ ik G By ' om we ZU: \ Bou bo & AE Er ee 8 B® IR , | . 4 tet 4 Bos ms 2 i eo an i” no a 2 i - - <