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Spencer gave me your question "Is there any connection between this and Bonner and Luning's results (Hereditas 1949,
52)?" to answer. Sorry we are so late.
There are two aspects to the question, aging and cause of loss of chromosome.
1a) Aging upon ring loss: Yes our work agrees with Bonnier and Luning's in that aging does increase the incidence of gynanders[?].
The difference is only indicated in their work as well as Petterson (1931) because they were using only rod chromosomes and
the rate of incidence is very low. The difference between aged and non aged in ours in highly significant perhaps because
of the naturally higher rate or perhaps because the aged material cytoplasm has more effect on the ring chromosome.
1b) We too found differences between reciprocal crosses but in contrast to Bonnier and Luning only in incidence of ring loss
- not ring and rod. However
there is a low incidence of rod loss in X-rod string genotypes and it may be that if we had a larger numbers we would be able
to detect this Ballacharya[?]
1949-50 (Proc Roy Soc Edinburgh) reports differences in ring loss in different genotypes I am just now doing crosses and
calculating data on this
2. Cause of loss of chromosome : Bonnier and Luning attribute loss to (a) single breaks in male (irradiated) chromosome and
to (b) a disturbance of the karyokineticmechanism of the egg cytoplasm which presumably acts on the movements of the chromosomes
in the first cleavage mitosis. " The first (a) we cant[SIC] argue about because we did not irradiate I know - from work
in Mullers lab - that there is a pretty high incidence of gynanders[?] (loss of Xc2) after irradiation of the Xc2 male but
I'm inclined to believe that a large part of this was due to aging of the females before mating
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(we collected them over a period of several days) and probably not due to breakage of the ring by the X-rays.
I do not agree entirely with B and L on the second point i e ..."1st cleavage of mitosis." However this is in part
my inclination to idea that if the loss occurs at the first cleavage the gynander will be I bilateral. And if at later cleavages
only part [TABLE] of the individual will be mosaic. The other theory (II) is that the amount of 1-X tissue will depend upon
the angle of the metaphase plate at the first cleavage. This as near as I can see presupposes that loss occurs only once.
All of our data suggests that losses do occur later as well as at the first division. This is a point we are worried about
ourselves for several reasons. Logically I don't see how there could ever be a bilateral gynander because of the method
of nuclei and cellular formation. All nuclei are formed first in the middle of the egg then they move out to the periphery
and cell walls are formed. It seems to me that the fily[?] should be spotted for female and male tissue - but they arn't[sic].
If loss occurs at the first cleavage and is due to misfunction of karyokinetic mechanism then it seems to me that instead
of gynanders the individuals should be males. Why is only one ring lost If it has already become two chromatids before entering
the egg ? If the cytoplasm causes misdivision of the ring (so that it became a dicentric for example) both rings would again
be lost. There is some evidence that there are proportionally more males than females after aging but I'm not sure that
this is due to an increase of X0 males (resulting from loss of the ring or both rings). I am testing this now. It may be
that gynanders or mosaics do not survive as well as females or XY males.
If I havent[sic] answered your questions I would be more than glad to correspond in greater detail with you about it.
My best regards to your wife and everyone at Wisconsin