Letter from Barbara McClintock to Charles R. Burnham
McClintock referred to this note as an "appendix" to the letter to Burnham dated July 30, 1931.
Item is handwritten. Item is a photocopy.
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2 (138,419 Bytes)
1931-08-08 (August 8, 1931)
Burnham, Charles R.
Original Repository: University of Minnesota, University Archives. Charles Burnham Papers
Reproduced with permission of the University of Minnesota, University Archives. Charles Burnham Papers
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Letter from Barbara McClintock to Charles R. Burnham (July 30, 1931)
Box Number: 3
Folder Number: 4
Dear Charlie --
This is just an appendix to my last. I have a correction to make in one case. I wrote you about a case of AB Pl female and
pl male which had been x rayed in early embryo and had given rise to a plant which looked ABpl (all other plants in culture
were distinctly purple) and therefore indicated that pl had been lost. I also wrote that examinations showed no visible change
in the satellite chromosomes. When the plants tasseled the anthers were distinctly purple -- the plant, therefore, was probably
ABwPl probably or AbPl. There had been, therefore, no loss of Pl and no change was expected, then, in the satellite chromosome.
There are no cases which we have examined, true, that show a "mutation" of one of the known genes that has'nt
[sic] shown a visible change in some way -- Correction completed!
[END PAGE ONE]
[BEGIN PAGE TWO]
The pl deficiency involving an interchange between the satellite chr. at the region of Pl with another chr. is not going to
pull thru, I believe. The plant is nearly 90 percent sterile. I have been working on it and find one very interesting feature.
In the chromosome other than the satellite which is involved the insertion regions do not correspond [diagram along left side
of page] -- In one chromosome (do not know whether it is the interchange or the "normal") its insertion region is
nearer the cross. In the other it is farther away. The slides are very clear on this point. One of the chrs. may have an inverted
section. There is an occasional looping at this region in the chromosome but I can't make out details. I have made the
diagram as a close cross, however, this probably doesn't occur and hasn't been noticed -- it shouldn't be expected,
either, if there has been some loss at this region. I believe this non-correspondence of insertion regions will be found in
species crosses. It may explain why morphologies vary in nearly related forms where number is constant.