1022-7954/04/4007- © 2004
Russian Journal of Genetics, Vol. 40, No. 7, 2004, pp. 723–731. Translated from Genetika, Vol. 40, No. 7, 2004, pp. 893–902.
Original Russian Text Copyright © 2004 by Chadov, Chadova, Khotskina, Artemova, Fedorova.
Chromosomal mutations, or rearrangements, are
widespread in animal and plant genomes. They are
undoubtedly involved in the process of speciation.
A great number of works are devoted to rearrangements
or conducted with their use. However, the currently
known functional signiﬁcance of rearrangements is
rather low. Rearrangements alter crossing over  and
lead to position effect variegation, i.e., a change in gene
activity on the boundary with the heterochromatin .
On the basis of only these properties, it is difﬁcult to
explain the wide distribution of rearrangements.
It has often been assumed that rearrangements lead
to large-scale alterations in gene expression. This
assumption enters basic biological hypotheses [3–7].
Changes in expression caused by rearrangements were
actually recorded by many authors [2, 6, 8–11]. How-
ever, a far larger number of facts suggest the contrary:
genes are expressed irrespective of rearrangements.
Marking of chromosomal rearrangements with visible
mutations is a standard procedure in genetics. On the
basis of obtained results one can conclude with conﬁ-
dence that in many cases, no changes in expression of
visible mutations occur in the rearranged genome.
In 2000, a new class of
ultative dominant lethals) was obtained [12–14]. These
mutations in the X chromosome are not lethal in the
male genome. However, when the males were crossed
with females of the
strain, the dominant lethal
effect of mutations was observed: no daughters
appeared in the progeny. The mutations manifest a vari-
ety of unusual properties [14–17]. They were assigned
to mutations of regulatory genes controlling ontogeny
[15, 17, 18]. The expression of the facultative dominant
lethals proved to be sensitive to the presence of chro-
mosomal rearrangements [14, 17]. Using this property,
we developed a method of search for mutation in
autosome 2 . It was supposed that the
main target for the action of rearrangements are regula-
tory rather than structural genes which have thus far
been principal participants of genetic experiment.
In this work, the effect of rearrangements on the
expression of mutations of regulatory genes was stud-
ied. Primarily, the effect of rearrangements inherited
from the mother on the expression of mutations
received from the father. Mutations were facultative
dominant lethals [12–17]. Next, the effect of rearrange-
ments received from the father cell on the expression of
mutations received from the mother was examined
. In this case, the mutations were recessive lethals
of the X chromosome obtained by the classical Muller-
Chromosomal rearrangements drastically changed
the expression of mutations of regulatory genes. Rear-
rangements either caused the lethal mutation effect or
suppressed the already present lethality. Thus, the chro-
mosomal rearrangement is very important for deter-
mining the pattern of genome functional activity. In
addition, wide distribution of rearrangements in indi-
vidual genotypes and their effectivity in the process of
speciation may be explained.
MATERIALS AND METHODS
The study was conducted on
A collection of mutations of regulatory genes
The Main Effect of Chromosomal Rearrangement
Is Changing the Action of Regulatory Genes
B. F. Chadov, E. V. Chadova, E. A. Khotskina, E. V. Artemova, and N. B. Fedorova
Institute of Cytology and Genetics, Russian Academy of Sciences, Novosibirsk, 630090 Russia;
Received June 18, 2003; in ﬁnal form, November 11, 2003
—Effect of chromosomal rearrangements on the expression of mutations was studied in
regulatory genes. These were facultative dominant lethals and recessive lethals on the X chromo-
some obtained by the classical Muller-5 method. Chromosomal rearrangements drastically changed the expres-
sion of regulatory gene mutations. Rearrangements either caused the lethal effect of mutations or suppressed
the already present lethality. The action of rearrangements exhibited the maternal or paternal effect. Irrespective
of the presence in the genome of mutations of regulatory genes, a rearrangement acted as a factor decreasing
fertility of the organism. The rearrangement effect is identical to the expression of regulatory genes per se. It is
concluded that the chromosomal rearrangement affects the examined regulatory genes indirectly through a
change in the operation of regulatory genes located within the rearrangement. Thus, rearrangements gain great
importance for the deﬁnition of the pattern of genome functional activity. Widespread distribution of rearrange-
ments in individual genotypes and their effectivity in the process of speciation are thus explained.