abstracts of papers presented at the 1962 meetings - Genetics

ABSTRACTS 969
procedure leaves much to be desired both in the retention of stain by the chromosomes, and in
the time required to obtain a permanent mount. We suggest that better staining of chromosomes
may be obtained with a simple modification of the conventional Gram stain employed in bac-
teriology. Air dried chromosome preparations on slides or cover slips are stained for 75 seconds
with one percent crystal violet, washed thoroughly in tap water, mordant with Gram’s iodine
for two minutes, washed thoroughly, counterstained for five seconds with safranin, washed thor-
oughly and air dried. The essential modification here is that no decolorization with alcohol is
employed. The air dried stained slide preparations may be observed directly under oil without
cover slip, or may be coverslipped with a drop of Permount without a dehydration sequence. With
transmitted light the chromosomes are purple to blue. With a green No. 58 filter in the light
path the chromosomes are a clear full-bodied black with little or no background evident. With
phase optics the chromosomes are a brilliant light blue with a pink background. The density of
staining and the contrast obtained with this modified Gram stain is superior to that obtained with
acetic orcein. (This investigation was supported in part by Grant No. 261-1 from the National
Multiple Sclerosis Society.)
MCDONALD, D. J., Department of Biology, Dickinson College, Carlisle, Pa.: Characteristics of
Tribolium populations in equilibrium.-Different strains of Tribolium confusum were reared in
population cages from which weekly estimates of natality, mortality and adult population size
have been made. These populations, in contrast to others previously studied, attained an equilibrium
size which was different in the two strains observed. Four populations of one strain, derived
from a recently collected wild stock and a laboratory stock, attained average sizes of 2076, 1972,
1954, and 1860 adults, and natalities (number of pupae enclosing per week) of 221, 186, 183, and
204. From these data the mean longevities were calculated to be 9.4, 10.6, 10.7, and 9.1 weeks.
Two populations of a second strain, derived from the wild stock only, and containing the eyespot
(es) mutation and its wild allele, reached average sizes of 2539 and 2388 adults. The natalities
were found to be 391 in both cages and the mean longevities are 6.5 and 6.1 weeks. It is suggested
that the higher natality found in this strain leads to the formation of larger populations in which
more adverse conditions result in shorter life spans. Since all the populations are maintained in
similar environments, dissimilarities in population parameters probably reflect underlying genetic
differences in the two strains. The only visible genetic difference was the presence of es in
the populations of the one strain at a frequency of 0.67, and since there was little change in
frequency during 130 weeks it is possible that the es mutation and its wild allele are in genetic
equilibrium in these populations. (Supported by National Science Foundation Grant G-8888.)
MCGINNIS, R. C., (Introduced by I. A. UCHIDA), Department of Plant Science, The University
of Manitoba, Winnipeg, Man., Canada: The occurrence of spontaneous aneuploids in common
oats, Avena sativa.-In an attempt to produce an aneuploid series in common oats, Avena sativa,
seedlings of foundation lines of the variety Garry were examined for chromosome number by
squash preparations of Feulgen stained root tips. A total of 4,023 seedlings were examined and
24 spontaneous aneuploids were found comprised of two nullisomics, 17 monosomics and five trisomics.
From karyotype analysis it was determined that all five trisomics are different from one
another and there are at least six and possibly eight different monosomics. Fertility was markedly
reduced for all aneuploids. Three of the monosomics and the two nullisomics were completely
sterile and were never identified. It appears probable that a trisomic series will be more easily
maintained in this species than a monosomic series. Limited data on univalent transmission indicate
wide variations between different chromosome lines.
MCNARY,
H. W., and A. E. BELL, Purdue University, Lafayette, Indiana: The effect of en-
vironment on response to selection for body weight in Tribolium cmtaneum.-Two populations
of Tribolium cmtaneum originating from the same random mating base population were cul-
tured in different environments and selected during nine generations for increased body weight