ISSN 10227954, Russian Journal of Genetics, 2012, Vol. 48, No. 4, pp. 473–476. © Pleiades Publishing, Inc., 2012.
Original Russian Text © V.G. Zainullin, E.A. Yushkova, 2012, published in Genetika, 2012, Vol. 48, No. 4, pp. 561–565.
The consequences of a chronic exposure to low
intensity factors, especially ionizing radiation, for bio
logical systems are of particular interest of modern
ecology. It was demonstrated that the response to
exposures is mediated predominantly by certain regu
latory mechanisms based on transpositions of mobile
genetic elements (MGEs) . Transposition activity
of mobile elements is believed to be responsible for the
majority of spontaneous alterations and genome insta
transposon is well known among many
mobile elements and is found in
fish, birds, mammals, and even humans [3–5]. The
element is classed with activatortype transposons.
element mobilization is observed in crosses of cer
strains (P–M hybrid dysgenesis) and
in response to environmental factors, including irradi
ation [6, 7].
element is known to have high affinity for the
locus, which is destabilized in the presence of
transposase expressed from the fulllength
copies [8, 9]. The majority of studies on radiation
induced activity of the
element focused on the con
sequences of acute irradiation [10–13].
In nature, populations are exposed mostly to low
intensity factors. It was noted that global and local
increases and decreases in mutability of individual
genes as a result of transpositions of MGEs, including
transposons, may arise in such conditions [14, 15].
The objective of this work was to estimate the
element activity levels, inferred from the instability of
from experimental (synthetic) populations and labo
ratory strains differing in cytotype after a chronic
exposure to irradiation.
MATERIAL AND METHODS
We used the following
Canton S was a wildtype strain that lacked
in the genotype and had the M cytotype .
Harwich was a wildtype strain that contained full
element copies in the genome and had the
cytotype [17, 18]. The 3001 laboratory strain (geno
) was homozygous for
mutation, carried two defective
elements in the
locus , and had the
M cytotype . The strain was utilized in mass
crosses to estimate the mutability of the
laboratory strain (genotype
) had the attachedX chro
mosomes and expressed morphological characters of
, yellow body),
, white eyes) mutations. The
strain was used in individual crosses to estimate the
mutability of the
Construction of model overlapping P + M popula
tions by introducing males with
in an M population (Canton S) to 1% was described in
detail previously .
Flies were chronically exposed to
source (56 mGy/h). Overlapping
populations were irradiated at an exposition
dose rate of 0.31 mGy/h (an accumulated dose was
100–112 mGy per generation (14–15 days [23, 24])).
In experiments with laboratory strains, males of the
Canton S and Harwich strains were exposed at a dose
Estimation of the Levels of RadiationInduced
and Laboratory Strains
V. G. Zainullin and E. A. Yushkova
Institute of Biology, Komi Research Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, 167982 Russia
Received August 10, 2011
—When experimental P + M populations were exposed to chronic
irradiation (0.31 mGy/h), the
highest instability level of the
) locus was observed in F
with a subsequent decrease and
stabilization of the mutation rate. The
mutation rate was within the range of spontaneous variation in con
ditions of P–M hybrid dysgenesis and irradiation of males of the Harwich laboratory strain with active
ments at 1.61 mGy/h. The instability of the
locus was significantly higher at lower dose rates (0.23 and
0.31 mGy/h), suggesting a nonlinear dose–effect relationship.