GOUCHER COLLEGE
BALTIMORE. MARYLAND

DEPARTMENT OF BIOLOGY

Earth 2, 1940

Dr. Barbara McClintock
Dept. of Zoology
University of Missouri
Columbia, idissouri

Dear Barbara,

      I am enclosing, after so long a time, your drta on the seg-
regation of heterozygous translocations in maize.  I?urnhax, at the
Christmas meetings in Columbus, told me thrt he was planning to do some
further work on this problem, and that you had promised to send your
data to him.  I am very glad that someone Xorking in maize is going
to continue work on the problem.  I am still vel?J much interested in it
myself. but have temporarily laid it aside until I can compiete the
study of the comparative susceptibilities to X-ray trent:nent of the mz&z
chromosomes in the zle and female germ-cells of Drosophila.  Per-
haps by the latter half of this year I car get back to it. Yo:?r data
interested me so much tlat I was unvrilling.to return them until my
secretary had made a copy.  Ffterwards I had to check them for accur-
acy, and r:hat rrith an experiment in progress, a pressing editor, and
the flu, it has been imnossibie to get them off before now.

      There are one or t$:o tiiings concerning which I have questions.
(IIn 6-lOT, hour do you know that among; the crossovers, the frequencies of
orthoploid and aneuploid 1 gametes are equal?  I didn't find the.
statistiw.1 data for this conclusion which is a very interes-tine  one.
@IP 6-5Ta, what vsas the pollen sterility?  .@Farently it :7as 505 a-
mong the non-crossovers.  EOK did it lF:ork o!l-t smon~; the crossovers?
@I am sti1.1. unable to see why a symmetrical equal-nr#med cross
with the spindle attach!lent 9'                     figure,
                         et the intersection of the cross x would
logically yieid one orthoploid: one aneuploid 1: one anj&Floid 2. I
should expect to set the ratio 2: 1: 1,  as in the translocations 1
studied in Drosophila by Dobzhansky end Startevant.
                                                       my
       On the whole, I think your data fit in very v:ell .i;ith ti hy-
po-thotical analysis of the factors controlling segregation. There rc-
mains the question o.f the influence of t!,e location of spindle attnch-
ments in conjunctionwith crossing over in interstitial regions ?z&ere
the chiasmata cannot terminalize.  I hope to keep in touch r:rith 3urn-
ham, and look forward to getting more light on these points.

     Suzanne would send her regards if she knew I were irriting.
We often th:_nk of you, and the pleasant times we had together in Col-
umbia.  For my part I heartily wish I still had the stimul.ation I
got from dropping in to talk things over -;;ith you.

Best segards,