che hate, ee - 3 November 1947.
Dear Ed- a

| a Reo'd your post card just after sending my last hasty note.

_ ‘"Binked segregations" is due for the September issue of

- _Geneties. ‘Theytye had page prwof back for over a week now,
"but there 1s still no telling when 1t will be in print.

K-12 has the following sugar formula: _ Me
| Lactose + a . . a
.o> Maltose’# >. | mo oe - eo co
-.. Galactose + (contains bath + and - cells in Monod's senee)
. Sucrose = (all efforts to obtain Sucr+ have so far failed) .
“ Gellobiose =~) 2 2 aan
“+ Melibtose + (but rather weak). .

‘Sorbitol + °C se UE DE ES
; “Duloitol + (+ mutants easily obtained by selection) —
ote Soe Rylose #7 Loe ae ET, ce
wos 2 Avabimose PUN gee.
oo... = "> Rnemese + (slow) - pe ee
“.--a@emethyl glucoside «- ee . ae
- “oo ST have @ slue of Gal-, Malt- and lac- now, using HN2 as the-2.°
- (presumed) mutagenic agent. I'll send them on shortly. As far as .
tested, they are specific, but I don't have the range yet of
synthetic substrates that I would need.. My big stumbling block
so far is getting reversions for sucrose and for a-methyl glucoside.
Working out the theory for the most efficient dose to use to have
the maximum total numbex (not proportion) of mutants among the sur-
vivers of mutagenic treatment, the answer comes out the dose that
leaves 1/e or 36.8% survivors. Beyond this point the proportion of
_ mutants continues to increase but the absolute number falls. This
. . Walue is independent of the rate of mutation provided that the =
’. Spontaneous mutants originally in the culture are demnored. = 2 oe.

  

Ly ee Us a eet .

  
  

 

| “| Qn the last few tests here, .Y53 seems to have lost the gapagity
‘to revert to Lac+. I- would appreciate it if you could send mea: |.

~ AyopUtd tube of earliest dates oc) Spd SER ete
A letter from Witkin wherein NaCl 4s described as the most ef-. -.

a rn eT

_ Fioient mutagen (at toxic conc.) yet testeds ~~