Wolfram Heumann September 26 14957
849 Frospect Flace
Madison / Wis.US&

Frofessor DreJ.Lederber é&.
Dept.of Bacteriology, Univ.of Melbourne
Carleton N34

Me 1 bouron e,australia.

Dear Josh!

Your and Esther's descriptions from your travel and the first days
in Australia have been very interesting and enjofing to read for me.I hope
all the things go further very well and you have an excellent work in
a pleasant time.

In the last experiments I get evidence for recombination between
Be - mutants.I have crossed:

rs sm? pol¢+ x rk sn® pol-
and I get the recombination:r R Sm™ pol-.The cross has been grown in
nutrient broth tubes.The selection has been made in nutrient agar plates
with streptomycin. the recombinant colonies grow very cleargm® against the
rs Sn? pol+ background,they are stable.I get never any rR sm™ colonie
in the control tubes and plates,made in the same number, as crosses were
done.IThe recombinant frequency,expressed in r R sm’ colonies is 1 re-
combinant in about 10 ooo cells.If I put the tubes in the rotator ,I
get this rate in 5 days,if I place the tubes without momvement,l used heut
9 days for this result.In the rotator the star forming cells settles
in a ring at the tube wall.The microscopic examination of these cells
shows very dehse stars,cell~fusion ige hae gkar center is often obser-
vable.But the most stars are formed"either from pol+ or from pol- cells,
seldom mixed stars are discernibly.This may explain the relatively low
rate of recombination. Now from these experiments I have Sm™ mutants in
both mutant groups,pal+ and pol-, and I will establish crossings separate
in the pol+ and in the pol- group,hoping I get then a hizher recombi-
nation frequency.
~?2-

Beside these experiments,I performed earlier same other crosses
with other mutants.Par example: 1 SxrR. I get the recombinant 1 R
about 1 in 10 ooo.But there are two disadvantages:first it is ditticult
to select the 1 Kk mutant against the parental backsround,and second:
the mutation rate from rR to lRe is about 1 in Joo ooo.I think it is
m@&ch more convenient and conclusive it the 8m" mukaxk marker is involved
in any crosses.

Now I am twice sad to leave with regard to these first results.
My position in Germany requires to m@tch routine work cutting down the
time tor research.But I would be very happy and I hope still I xet the
occasion to meat you in Germany in your return-journey.[h@n we could
sveak over the research progress and the results obtained in the last
experiments. We leave Madison Oktober 48% and will be in Braunschweig
November first.iiy address there is Botanisches Institut der echnischen
Hochschule.Fhone Number: 2 0191,ext. 213.

finally I say you ones more my best thanks for all your help and
advancement.I have learned to go in your lab,and if I made progress then
it is your merit.I send you for good bye s@me pictures, but unfortunately
the colores sre much more bad,than in the slides,

With the best recommandations to usther and greetings trom Barbara

I am sincerely yours

—
fo”
1.)The symbols of the mutants: °*) the pictures:
r= red 1.= Madison from governors island
l = white ‘ ae= Lake wendota from Prospect Fl.
R = rough 3.= Barbara and Irene.In the glass ed
S = snooth is a turtle Barbara just has caton

Sm= streptomycine
pol=pol-bodie

4.= I

5e= Dodecatheon meadia,shooting star
6.= Cypripedium acaule,mocassin flower
7-= Cypripedium arietinum,ram's-head
Lady 's-slipper.