Evening star., 1955-02-07
Mice Better Than Flies
In Reduction Studies
Greoter Mutation Rute
Aids Genetic Research
BY Thomos R. Henry

The mutation rate in mice subjected
to heavy radiation Is 10 times that OF
fruit flies, the animals usually en-
ployed in genetic experiments.
"A mutation" is q permanent heredi-
tary change In family line. some
times very slight and sometimes quite
noticeable. 1t generally is agreed that
at least 90 per cent Of all mutations in
any species are bad. although over
many milleniums the rare good ones
have been the major factors In evo-
luton.
Finding of the enormously greater
rate in mice-mammalS, and hence Tar
more comparable to human beings than
are fruit flies-has been made by Sci
entists at the Atomic Energy Commis-
sion's Oak Ridge laboratory. according
to a report recently issued by the Acc.
The findings, the Acc admits. have
made it necessary "to revise estimates
Of the genetic hazards of radiation IN
man."
Fatal Doses.
Oak Ridge mice, according to the re-
port, were subjected to far heavier radi-
alton than a human being ever would
be likely to get in a single dose. or
even ordinarily in lifetime. Received
on only one occasion, it probably would
be fatal. The experiments with mice
will be continued, according to the re-
port, to determine the genetic effects
of such doses as man or woman would
be likely to receive.
Almost all conclusions in the past
have been based, apparently quite
naively, on fruit fly experiments be-
cause Of the many generations Of these
insects which can be raised in q
single year. Thus genetic effects could
be determined in a reasonably short
time. Experts always have realized,
however, that the insect was far more
stable animal, from an heredity stand.
point. than any mammal.
It has been claimed, although not quite
established, that q man Is about ten
fold as susceptible to genetic damage
as .mouse-the same difference shown
between a mouse and fruit fly; but
this always will be extremely difficult
to prove because of the length Of the
human generation.
The question has come prominently
to the front in the past few months in
connection with the possible danger Of
"fallout" from experimental atomic
bomb explosions and with the atmos-
pheric contamination that might fol-
low large-Scale installation Of atomic
energy plants.
Study Of Natives.
In the same report the Acc tells Of
a medical follow-up study of inhabi-
tants of Rongelap and Utirik, two Of
the Marshall Islands, who accidentally
were exposed to the fallout from one
of the South Pacific bomb explosions.
Within a few months, the Navy doctors
who carried out the survey found. the
overt effects on these natives largely
have disappeared. They now appear
to be in excellent health. Blood counts
are normal. Skin LESSONS have healed
entirely and there has been re-
growth of hair which fell out after the
exposure.
Admittedly. however. this reveals
nothing about the possible genetic
effects which will not be apparent for at
least another generation. Some may not
show up for four or five generations,
many geneticistS believe.
Nobody knows just how the genetic
effects result from radiation-whethe
primarily through chemical changes in
duced in the germ cell or by breaking
and rearrangement Of the strings of
genes, units Of heredity, known az
chromosomes The Acc scientists are
seeking to throw some light on this by
studies of one-celled organisms-bac-
terra and protozoa.. Experiments also
are being carried out with yeasts.
moulds and such higher plant organ
iSms as corn.