McClintock developed a close professional relationship with Green following his discovery in 1967 of transposition in drosophila.
Because his findings were at first not widely accepted by many geneticists, Green asked McClintock to determine if there were
problems with his findings. This letter is representative of their exchanges after this date.
Number of Image Pages:
2 (165,601 Bytes)
1968-02-27 (February 27, 1968)
Original Repository: American Philosophical Society. Library. Barbara McClintock Papers
Reproduced with permission of the Barbara McClintock Papers, American Philosophical Society.
Medical Subject Headings (MeSH):
Gene Expression Regulation
Controlling Elements: Cold Spring Harbor, 1942-1967
Box Number: 1
Folder Number: 7
February 27, 1968
Your letter of February 6 reached me the day before I left Cold Spring Harbor for Austin, Texas, to give a set of lectures.
I returned from Texas a week later with a blooming cold and much fatigue. Both conditions are now relieved. They account,
however, for the long delay in replying to your letter.
I was delighted to receive an outline of your recent progress and very much pleased with the results. One aspect--the placement
of the controlling element associated with wc--resembles that of Judd with wzm and its derivatives. In both cases, the "controlling
element" lies within a common region of the white locus. I noted this initially in reviewing Judd's abstract that
appeared in the July, 1967, issue of Genetics. In a recent talk with Judd at Austin, I learned that in his case, he is finding
something strange at the white locus in salivary chromosome examinations and he, also, is not able to interprete its exact
nature. From this conversation I gathered that you know of his recent results and therefore, I need not recount them.
The similarity of placement of the "controlling element" in the wc and wzm cases conforms with the cases in maize
where different known systems have taken over control of gene action at the Wx locus. The tests of this were conducted by
Oliver Nelson. He is now writing up the results of a large number of tests aimed at placement of sites of change within the
Wx locus that are responsible for mutant expressions. Most of the mutants were "spontaneous" in origin. A few were
produced by X-rays. Both multisite and single site mutants are represented among these selections. In addition, five cases
of change in gene action induced by the presence of known controlling elements were included in the site mapping tests. One
multisite (deficiency type) mutant covers a segment within the locus that is close to its middle. The controlling element
in each of the five cases lies within this region of the locus. Three of the five cases are independent inceptions of control
of action of the Wx gene by the Ac system. A fourth is a stable mutant derived from one of these. The fifth is an instance
of control by the Spm system. When homozygous none of the five cases gives rise to a wild-type allele. Also, the stable mutant
when combined with the mutable allele from which it arose gives no wild-type alleles. Otherwise, each combination gives rise
to a few wild-type alleles. It has been possible to order the sites within the controlling element region that distinguish
one allele from another. There is no evidence that the different alleles of the c.e. alter crossover frequencies within the
locus when combined with alleles derived from spontaneous mutation.
Nelson plans to send the manuscript to me sometime this coming spring. I will then have more precise information. Just now,
I have only the detailed information that was available from tests conducted up to April, 1966. These are the data that I
showed to you this past June. Some of the more recent information given above comes from a telephone conversation that I had
with Nelson several weeks ago.
When I have the needed details, I will send you a summary. I am sure Nelson will allow you to refer to his yet unpublished
work provided you send him a copy of your statement in order that no misrepresentation appear in it. Peter Peterson has an
abstract in the July, 1967, Genetics I which he refers to Nelson's results. His statements, however, were incorrect and
misleading. This was disturbing to Nelson (and to me). Peterson did not check with Nelson before submitting the abstract.
Again, many thanks for keeping me informed. It is much appreciated. Also, give my very best to Katie.