d. The great majority of mutations, spontaneous and
induced, are to some extent detrimental, although the
Geleterious effects in a large fraction of all
mutations do not show up for two or more generations,
e, Present information suggests that only a fraction
of naturally occurring mutations are attributable to
natural radiation.
3. Information necessary for good estimates of the genetic
effects of radiation on humans is difficult to obtain for at
least three reasons:
a. Direct observations on humans cannot provide
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sufficient information,
It is not possible to use
such experimental procedures as planned radiation
exposures and matings.
Generation times are too
long, especially since observations extending over
@ number of generations are necessary to assess the
effects of induced changes,
The relatively small
numbers of offspring per couple make genetic
analyses difficuit, and reliance must be placed on
statistical approximations based on assumed
similarities in large numbers of couples,
b. Species for which experimental procedures are
appropriate differ among themselves and from man in
ways which make it difficult to extrapolate from
opserved response in one svecies to predicted
response in another,
For example, experimental
species differ in the following respects:
(1) The rates at which mutations are induced
by radiation.
For comparable doses,
induced
rates in mice are 15 times as great as in the
fruit fly Drosophila, and many times greater
still than in bacteria,
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:
a
(2) The relative sensitivity to mutation at
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one
different developmental stages of the germ cells,
(3). Length of the period during which mutations
may accumulate, from birth to the end of the
reproductive period,
ec, Great quantities of information must be collected
and analyzed,
4, The Commission supports genetics research at an annual
cost of approximately $2 million,
The research includes 2 wide
variety of investigations being performed under approximately
55 contracts,
ar
Dante WTT