Sstituto Neroterapico Silanese Serafino DLellanti

Mailsno - via Darwin n. 20
Telefoni N. 30640 30677 - 31757 - 32823 - 33917 Mileno, dan. 8th.1952.

 

Esportazione

Copici IN Us0:
A.B.C. 59a. & 6rn, Eprrion
Benrisy’s
Rupour Moses

Dear Lederberg,

Thank you for your letter of Dec 26th. I had heard
from you of your velvet technique and used a ereat deal of it in
the past six months,with the only modification that,in place of
velvet - no sufficiently thighy woven fabrics being available at
good prices, I have been using nearly always filter paper (Whaman
No. 1 or similar). Filtex paper does not seem to transfer apprecia-
ble quantities of substances from media to media,and the replica-
ting process is extremely neat. It is mounted on blotting paper
pads for kuz use on large square Petri dishes and on similar gad-
gets for smaller,ordinary size Petri dishes.

Your application to the demonstration of the mutatio-—
nal origin of resistant ijddivuduals seems very elegant .For chloro-
mycetin 1 had made recourse to a much clumsier,and involved method.
It seemed however to have made some ef“ect em tinshelwood when 1
told him of it last July. Hinshelwood seems to believe still now that
‘mutants may well be produced on occasions,but that most times a non-
mutational adaptation is taking place.

As to "heterothallism" : I agree that the use of this
word is premature, there being at present no trace of an opposite
mating type. The position is however that of the occurrence of self-
sterility in a strain,ahich is on the other hand cross—fertile with
akiaxkhex practically all other K-12 substrains, known to be homo-
thaliic. The accident mis} have occurred in the building of y-10,
however,and not in its unbuilding < when TLB, 4+ strains were prepa-
redfas kis sterility was observed with at least two independant
PLB + straincyone fron Y10 ona one from W 945, when crossed to
either Y-10 S* or to w945 SY or similar strains. What puzzles me
is that after recombination,no trace of sterility is found in tke

fxiiai offspring ; both TLB1-S? ana TLB1+ recombinants are fertile
Sstituto Neroterapico Silanese Serafino DLeblanti

Milano - via Darwin n. 20

Telefoni N. 30640 30677 - 31757 - 32823 - 33917 Wilen 0
a,

 

Esportezione

Copici In uno:
A.B.C, 57a. & 61x. Eprrion

Roos Mews among themselves and with appropriate TLBy@ parents. 4 similar
loss of a vegetatively stable character had been observed “or
Hfr. - Even if the use ef the word heterothallic is premature, which
other word should be used ?% incompatible is perhaps less compro-
mising,or rather self-incompatible. Also, i do not see how diffe-
rential fertility could explain the results ; 1 find little diffe-
rences of fertility in dhe various crosses mentioned,except that
in those betwean TLB, strains no recombinants nag ever been found.

Of course 1 should be interested to have lirs.Lederberg's

Behe sterile strain. If,as it seems sofar,it $22" penave as the
others, one should think that the mutation involved 4s a recurrent
one, using Drosophilists' terminology: 1 have had myself after Ny-
treatment a BM- sterile strain,which is now being analysed. I
should also be grateful if you would send me strains 58 ; 679 ;
679-680. If itrs.Lederberg's strain is available,could you let me
know tine story of it.

On crossing TLB,- filial strains 1 have found some of the
abnormalities which you mention . It seems to me that Y-10 is
exceptional under mafWays; perhaps some,or all of its peculia-
rities can be recondufed to one cause.

As to BM,recovery of prototrophs by mutation does att
seem easier on biotin agar. But I doubt that mp Rasta may be
slightly toxic,because I have at present difficulties with any
back-mutation(but not with recombination!).

Re the Genetics Congress; = know that the Secretary counts
to propose your name for a major paper, gnd that it is paanned to
give some financial help to allx those who will be so asked; but
unfortunately the help is bound to be poor. If there is anythigg
in the way of official invitations etc. which we can do from here,

and that could help you to provide local financial support plea

%
let me know.

>

Yours sincerely

a
: i
oe Thott Bae niente preete
»
ne Ee .
* X
+ ©
y
i
.
‘