- il .
chemical in nature.
Now if this be so, and the rac
duced mutaticns are nearly always caused by chemice
are produced in tne first instance by radiation, tk
tion ine
:
which
: cheni-
cals themselves which are not produced by radiation. out nave
other origins, can cause mutations, so it seems Lik: «y that a
major part of the natural or spontaneous mutations La any
species is not radiation induced. This point is an important
one to settle, for the reason that we have to compar ~ the
the natural
effects of fallout radiation with the fraction
spontaneous mutations which is due to the neguation we are
In other words, if the normal mutanormally subjected toe
tions are all due to radiation, then the effects of th
additional radiation from general test fallout, or from
other sources of radiation such as atomic power, or the
It
medical uses of isotopes and X-ray, will be larger.
seems likely, and many genetic authorities agree on genetic
grounds with this conclusion, that a major portion of the
spontaneous mutations of the human species is not due to
radiation but due to other causes. Therefore, a fraction of
the spontaneous mutations in the human species is taken as
Now, what this fraction is, it
being due to irradiaticn.
is difficult to say, but Professor H. J. Muller has estiTherefore, one estimated that this misht be 10 percent.
maves the 150 milliroentgens per year from natural radiation
now causes about 10 percent of the spontaneous mutations,
and therefore, that the test fallout if continued i:.idefinite~
‘dywill, at the present level of about 1 to 5 millircentgens
nor year, cause an increase in the natural spontanecus muta-
tion rate of something like 1/50 of ten percent, or 5.2 of
a percent of the spontaneous mutations.
In the extreme,
it should prove that all of the spontaneous mutation rate
if
is radiation induced despite the chemical argunents, the ef—
fect would be ten times as great, or two percent. Dr. Dunning
of the Division of Biology and Medicine of the AEC estimated
(The Scientific
1.4 percent in 1955 on similar assumptions.
Monthly 61, 265-December 1955.)
This effect is one which is
comparable to moving to a slightly different locality and is
much less serious than changing from one house to another or
The only important point is
doing any of a dozen things.
that genetic effects show only if large numbers of reople
Therefore, we would expect tnat the
are subjected to them.
effects of large populations changing their environ:.ent,
such as living at a higher altitude, or living inar
of naturally higher radioactivity, should cause genetic
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