Your reference to the McClintock paper is worth reading - you should do it. McClintock's paper is about the genome's response to challenge. She lists Heat shock and the SOS response as examples, but shows that there were others as well that were not well understood. She also shows how the activation of silent genes was part of her recognition of transposons. While she hints that there may be some mechanism for the breakage of DNA and its subsequent repair that today might be looked at as "fragile" DNA, she never mentions it as such. The concept is fairly recent and at the time of this paper (1984) she was in the waning years of her career and speculated about many things. The speculations of Nobel Prize winners are always worth listening to.
I don't think it's right to credit her with this, but certainly the seeds of the concept can be found in her studies and others as well. The current concept might be related, but is very much more advanced than what she was speculating about. Clearly the work on transposons was not directly related to genome challenge, other than through activation of the transposon. But the concept of "fragile" DNA is not directly related to the transposon. BTW I noted in an earlier post that at least some of these "fragile" areas were associated with high AT regions, i.e. "looser" hydrogen bonding. I wonder if this may play a role.
Great find, TH, I enjoyed reading the article.
Transposons are the original fragile DNA.
The genome rearrangement due to "stress" provides the mechanism for genome evolution and the analysis done in the context of non-random rearrangement.