UNIVERSITY OF LONDON

    

q ED

POSTGRADUATE MEDICAL SCHOOL
OF LONDON

" POSGRADMED CHISK LONDON DUCANE ROAD
Telephone ; LONDON, W.12
SHEpherds Bush $260 (4 fines) :

Department of Bacteriology. — 27 October,1952,

Dear Luca,

Thanks for your letter and the photographs. Most of them,
especially the group ones taken outside the Institute,are not very
good but the one including Pupa and Nora on the boat to Stresa is
excellent and we are very glad to have it. I am ashamed to say that
I have not yet despatched the toy motors. As I told you,I bought
a couple that were not so good. and promised to send- them off. I then
got two more of the better variety and they have been sitting on my
desk at home ever since, I have been very busy and kept saying to
myself that I would pack them at the week-end and something seemed to
happen and I put it off again! However,I promise most definitely to
get them off this week, Anyway,the later the children. receive them the
longer they will have them!

Watson told me of his scheme and has now forwarded to me a
copy of your analysis of it and I am struggling with this. My progress
in genetics(classical) since I last saw you may be judged from the fact
that I can follow most of it! It seems to me a clever concept and it
appears to fit the facts in general,though it does not seem to have any
“great advantage over your view (which was also mine,based on a somewhat
more naive foundation) that it is a part of a single F+ chromosome
which is invélved. I,of course,assumed that there was only one chromo-
some because the pundits had said so,but I am interested to hear that
you have. genetic evidence that,if this is really so,a break always
seems to occur in the same place. Could it be that the F+ agent is
an aberrant centromere which sometimes behaves in a "free-living" way,
sometimes carries that part of the chromosome on one side of it as a
kind of “tail",sometimes that part of the chromosome on the-other side
‘of it,and rarely the whole chromosome? This could account for your
Hfr findings if one supposed that in these strains the F+ "centromere"
was rarely,if at all,"free" and behaved in a reasonable fashion,as well
as for my evidence(which,I admit,is only suggestive) that the F+ agent
can occastonally act as a genetic aarrier. This,at best,is wild
speculation and probably nonsense,but I thi C
the whole business leaves plenty df room BERK you WT) admit .t abards
Jim's two chromosomes,he now seems to think that BM should be on-
chromosome B. This would seemg to account for the evidence of linkage
between BM & By, in Lederberg's 1°47 paper in which the method of
reversed crosses,which might be invalidated by F,was not used. I am
rather interested in trying a "ménage a trois" experiment(suggested by
Watson) using one F- and two F+ strains,to see if the F- parent can
acquire 4 & B from different gm F+ parents. The difficulty about this
kind of experiment is the existance of F+ transformations of the F= parent
and F- phenocopies(or whatever they are) in F+ clones,but I think this
can be got over by making pure F+ parents by SM-treatment. I have
succeeded in convincing myself that the only fertile mating is F+ X F-.

If “atson's hypothesis appears to fit the facts well I
certainly think that you and he should publish it jointly,but I cannot
see any possible reason for my mame being associated with it and would,
I think,prefer to have it omitted.

About the C,L &L paper. Unfortunately I have no copy of
the paper. Due to the rush about it prior to coming to Pallanza I only
had two duplicate copies made(one of which went to the editor) + thé
original typescript which I did myself. If Joshua is not going to
correct the proofs,could he sent back his copy(he could have a copy made
for himself) and you could then indicate to me on this copy what proof
alterations you wanted? I see no reason for you to feel embarrassed
at using the symbol "F" in the paper,no matter what the final interpretat-
ion of the nature of this factor turns out to be. I think it would be
very confusing to call it 6 unless this alteration is also made in the
L,C & L paper ‘in Genetics.. Moreover,"" is usually used to indicate
phage and there is no real evidence yet that. F is a phage(though I think
this very probable). My own feeling(anyway so far as my own paper is
concerned) is that it would be better to leave things as they are-as
properly representing our views at the time the papers were submitted.
If,then,you. shoudd obtain definite evidence that there is a locus for
the maintenance of F according to the kappa or lambda models,the
nomenclature can be changed. I cannot sce that there is any very definite
indication for change. at the moment or, that,should. things turn out as
you anticipate from the F+F- 1:1 segregations with your interesting
uninfectable F- strain,you need worry that you did not. foresee this and
incorporate it in a paper written a considerable time’ before. Of course,
if you and Joshua decide it should be changed that is quite alright but
I think you shou@@ then give reasons. for the alteration in terminology.
I think,however,I will let. ¥F" stand in. my own effort. a
"Streptomycinase" — I rung up Lightbown about this this mornihg. This
enzyme is produced by Ps.Byocyanéa but,I.fear,has no practical value.
It is highly insoluble so that large volumes must. be used to. neutralise
even quite small concentrations of SM. Moreover,it is itself quite
markedly bacteriostatic and,again,will not reverse sm the action of SM
which has already been in contaet with cells. It is really only a
laboratory curiosity. Lederberg was interested in it but Lightbown
considered it would be of no value to him either.

I am only just getting down to some bench work again,

having done nothing for over two months. I will let you-know anything
interesting that turns up. Best wishes to Pupa from Nora and.myself.

Yours ever,

ae