abstracts of papers presented at the 1962 meetings - Genetics

988 ABSTRACTS
treatment reduces the viable count of 0.1 of the original and induces a revertant frequency of
The amount of cold acid insoluble, diphenylamine reacting material (DNA) present in treated
and nontreated cultures is identical. Transforming activity of extracts prepared from MMS
treated cells is heat sensitive and about 85 percent of activity is lost after 1 '/e hours at 50C; DNA
from nontreated cells is unaffected and the activity of nontreated DNA is not sensitized to heat by
mixture with DNA from MMS treated cells.-Incubation of cells in amino acid supplemented
medium leads to an increase in extractable transforming activity. The increase in activity of
extracts from nontreated cells is accompanied by an increase in cellular and extractable DNA.
Transforming activity from MMS treated cells more than doubles on incubation with little or
no net DNA synthesis. The heat sensitivity of transforming DNA from MMS treated cells de-
creases after incubation of the cells.-Turnover of DNA in the absence of net DNA synthesis can
be demonstrated in MMS treated cells. C-I4 thymidine is incorporated by MMS treated cells in
an alkali stable, hot acid soluble form. Thymidine incorporation increases steadily in MMS
treated cultures without lag under conditions where the net DNA content remains constant or
drops slightly.-The experiments may be interpreted to mean that a small fraction of new DNA
of normal activity and heat sensitivity is synthesized by MMS treated cells using the alkylated
DNA as a template. (Work supported by a grant (RG 7816) from the National Institutes of
Health.)
STUTZ, HOWARD C., Brigham Young University, Provo, Utah: Asynchronous meiotic chromosome
rhythm as a cause of sterility in Triticale.-Very little chromosome affinity is evident in
meiotic prophase in the sterile hybrids Secale cereale x Triticum aestiuum and Secale africanum
x 2'. aestiuum. Good pairing occurs in the colchicine induced amphidiploids but fertility is low.
Precocious chromosomes in pachytene and diplotene, lagging chromosomes during anaphase I
and anaphase I1 and abundant micronuclei in microspores of the amphidiploids suggest asynchronous
meiotic rhythm of the parental chromosomes to be the principle factor contributing to
the resultant sterility.
SUNDER, J. H., A. H. Gibson Laboratory, Univ. of Pittsburgh, Pittsburgh, Pa.: Inheritance of
cholesterol metabolism in the rabbit.-Because of the high intrafamily correlation coefficient
and the direct response to selection on the total serum cholesterol value in rabbits, it is concluded
that cholesterol metabolism is under genetic control. As an inherited characteristic, it is probably
of the multifactorial or polygenic type.-Standard experimental procedures of feeding added
cholesterol to increase the total serum cholesterol and produce arteriosclerotic lesions as well
as injecting sodium heparin to lower the total serum cholesterol value elicits a variable response
when randomly selected rabbits from diverse sources are compared as a group. This variation
can be measured as maximum and minimum levels attainable on a standardized dosage, and
length of time to reach the extremes. While the latter is not as variable as the former, it is
significantly different. There was no correlation between the extreme indices and the time factor
in the animals tested.-Results of experiments now in progress will be reported testing the
intrafamilial and interfamilial correlation of the normal physiological value with the two
stressful conditions and their effect on the normal value.-Other contributory and related physiological
indices such as Ix31 retention, 1131 conversion ratios and total triglyccride levels will
also be compared in the normal and stressed animals.-It is hoped that investigation, such as
this, into more than one parameter of a metabolic sequence may help to clarify the variable
picture seen in some hereditary clinical syndromes.
SUYAMA.
Y., University of California. San Diego, La Jolla. California: Properties and apparent
homogeneity of a complementation enzyme in tryptophan synthetase system of Neurospora.-The
extract from a heterocaryon between two allelic td mutants (td-3 and td-104) can catalyze the
conversion of idole to tryptophan, whereas extracts from each mutant as well as mixture of the
two cannot. The activity in the extract from the heterocaryon precipitates at a higher ammonium