ISTITUTO SIEROTERAPICO MILANESE
“SERAFINO BELFANTI~

Ente Morale aggregato alla Universita di Milano

Direttore Scientifico: Via Darwin, 20 - MILANO

jeri TELEFONI: 30.640 - 30.677 - 31,757
Prof. Augusto De Barbieri 32.823 - 32.964 - 33.917 ~ 350.649

Telegrammi: SIEROTERAPICO - MILANO

Milano 8/8/53

Dear voshua,

Thank you very much for the photographs, T am very plea-
sed to have something"tanvible" to show to the incredulous people,
although of course I tmk/“it is better to reserve comments about it.
The photographs are beautiful.I have never seen bacteria as well as
in those. De Verbindungsbriteke are rather thin ; have you ever caught
nuclear bodies passing across ?

I hope you had meanwhile alrathcr chaotic)letter of mine.
Finks is gone away,the work is not ;et completely finished, but the
data already collected have been analysed almost entirely. A Rather
pexculiar conclusions seem to stem out of these, Prezygotic elimina-
tion of one (or the other) "arm¥ ,arms being divided by a "point of
maximum elimination"close to Hfr,between St and Gal (W 945) seems to
offer a better explanation of the data for the Ft x F crosses, No
prezygotic elimination seems to take place for F+ x P+ ,at least for
the right"arm" &tLac T, LT) in the lines employed, mkaxsaxnp Hfr x F-
seems to give a picture of postzygotic elimination which might be
expected if the elimination point behaved as a lethal. Yost of the
data in the literature,on prototrophs analysis,seem to be amenable
to interpretation on the bas&s of pre or post-zygotic (indistinguisha-
ble in the published data )elimination,centered at the usually constant
elimination point ref®ered to above. Whether this will prove just an
essay of solving a crossword puzzle in an apparently correct way ,but
with a fundamentally wrong solution, or it corresponds to something
physickally meaningful, I am not prepared to say. However,in interpre-
ting literature data ,the assumption of poor pairing whenever odd
crossover numbers between two selective markers are not selected for
seems necessary. At any rate,the Gal (W 945) - Hfr linkage seems
conclusively established ; a trace of a guupiamen gene complementary
fo this for Hfr behaviour ,located in the LT region, has been noti-
ced.

Concerning the iticrobiology Congress. The paper for

Chain should give no troubles.I shall have to shorten it to keep to
the time limits ; I imagine I shall insist only on replica plating
for the first part,and summarise evenly the second part. Concerning
the paper on recombination,of which I sent you an abbtract : 7 had
to assume your consent to it,having had no reply about it. Proof of
the abstract is enclosed. If you have any imoortant remarks about it
you should write or bette: wire to me »noping to be in time for get.
having the &#teration made. The paper should be handed over before

the end of the Congress; xm about 10 typewritten sheets are allowed
I shall certainly be unable to prepare it for that date,but .
am fairly certain that the paper would be accepted also at a
later date. If you think you would like to write it,and take
senior authorship in the written paper, = should be very plea-
sed if you did. I could in that case let you have,say,tn Sep-
tember, a summary of my data wuich T shall present to the Con-
gress,to be taken account of in a synthetic way,so that the
written paper could partially reflect things that were actually
said at the Congress, I have not yet a clear idea of what 7
shall actually say 3; if you have any suggestions, please do
let me have them in time !

Hfr : My impression is that Hfr is actually less effi-
cient in handing oveito progeny markers like B, and M, than
those of the right arm. We have recently had experience on the
fact that Hfr passes to the progeny the St marker with a rate
comparable,and occasionally smaller,to that of F+. However,I
am practically certain,from the early data , that B.+ is contri-

‘buted by Hfr far more efficiently than by F+ ; but that the ef=
ficiency is less than for TL. Whether Hayes has got the same
sort of Hfr that = had, cannot be said until direct comparisons
will be made. However, for the moment,I think the Gal-Hfr linka-
ge would be a good test. Almost all Gal+ progeny from Gal+Hfr x
W 945 is Hfr. Reverse was not done, @ few Gal-Hfr recombinants
detected in a Hfr StY cross having unferrtunately been discarded
accidentally,and being not easily reobtainable.

Cytology. If I can secure any decent collaboration on the
subject,next year, 7 shall try to follow your work,as in the
plans. Perhaps, as you have been so successful in it, you may
prefer to be alone az this job. However,as you may remember from
the warly correspondence,I hate some interest for it, even if I
have been so inefficient about it until now. I hope you will be
entirely frank about it.

Please give my regards to Roger Stanier
Yours sincerely
Liven.

P.S. I pass on to you a suggestion T had from Calef. To make
certain that Verbindungsbriicke are formed between Hfr and F-
cells you may mark one of the two parents with P32 and correlatek
Giemsa staining with radioautographs.

Bt TOP, Ta, ey 4: Chy Awa ie Fre