Loovetefects of Radistion (Dr. bellany)
(3)
Mutations-—processes by which germinal material changes in such a way that
@ new charecter-~-or one not previously knoWre-appears suddenly and is inherited without
further change.
Or at any rate, without further change until a new mutation occurs
rfeeting the same locus or trait.
The cause or causes of mutation have long been a puzzle.
fron complete and many questions are as yet unanswered.
causes of mutation, it should be clear that by
in mutation rate.
Investigations are far
In the discussion of possible
causes of mutation we refer always to chan
Just as the investigator using a Geiger-Muller counter estimates
redioactivity in terms of counts ebove background, so te gensticist measures mutation rE
as ge multiple of the base or natural rete,
hadiant energy:
Tronty-one years eso Muller demonstrated clearly that mutation
wate cen be increased by exposing DroSophila banana fly to X-rays.
Ultra-violet light w:
Sinee 1927, mutation rate changes followins exposure to Xerays, famm rediation
acd in « few instances to particle rediation (msinly beta) have been studied in a con-
able number of orgenisms ranging through the viruses, bacteria, plants and animals.
Increases un to several thousand percsit are not unusual.
This is one place, however, «
npressing resvlts in percentage may be a little Misieading.
“ith a base rate of {0-4 a
incvease cf 100% in rate would mean txo mutations in a million; 3000%, 30 in a million.
the tric: for the geneticist, is to find those few in a million.
There cen be ne reasonable doubt that at lezst one of the causes of mtation i:
ionizetion (from radietion) and change in energy levels resulving in a chemical chenge :
the genes.
saves:
ae
an
Other forms of radiant energy---Ultra-violet light aad very high frequency rad
Experimentation with ultra-violet light is complicated by reason of its small
penetrating power. Small but significant increases in mtation rates of Drosophila and
corn have been demonstrated.
Very high frequency electromagnetic fields have not been well investigated.
Significant changes in the lethe] mutation rate and other changes huve been demonstrate
in Drosophila, however,
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