1022-7954/01/3708- $25.00 © 2001
Russian Journal of Genetics, Vol. 37, No. 8, 2001, pp. 888–893. Translated from Genetika, Vol. 37, No. 8, 2001, pp. 1068–1074.
Original Russian Text Copyright © 2001 by Chubykin.
The formation of the chromocenter, which inte-
grates the pericentromeric regions of all
chromosomes, is nonrandom due to some speciﬁc prop-
erties of heterochromatin. Each chromosomal arm has
a pericentromeric site that forms an association with
another site of a particular nonhomologous chromo-
some. The lack of these sites or the presence of extra
ones causes a situation in which chromosomes are not
included into the ring structure of the chromocenter [1, 2].
Disruption of conjugation of homologs also results in
the formation of aberrant chromocenters [3, 4].
Undoubtedly, the regular structure of the chro-
mocenter is genetically determined. The chromocenter
is not formed in the
mutants . We described
insertion mutation disturbing the reorganization
of chromocenter . In the present work, the
tion obtained by selection of mosaic clones and charac-
terized by abnormal cytokinesis and the presence of
two or (rarer) three chromocenters was examined . It
is unclear whether this is caused by premature reorga-
nization of chromocenter or its abnormal formation.
MATERIALS AND METHODS
In this work, I used 3-day-old wild-type
females (line Canton S) and hetero- and
homozygous females for mutation
is described in detail in .
Squashed preparations of ovaries were made using
Nokkala’s method with our modiﬁcations [1, 8]. Peri-
centromeric heterochromatin was differentially stained
as follows. After Feulgen staining, slides were thor-
oughly poured by glacial acetic acid and heated at
C for 1 min until dried up complete
drying. Next, slides were stained with a 2% Giemsa
solution in a phosphate buffer (pH 6.8) for approxi-
mately 20 min, which was followed by routine proce-
dures [1, 8]. This method of differential staining, com-
pared to that described earlier , yields good results
even at late developmental stages of oocytes, when the
nucleus is condensed into the karyosome and the chro-
mocenter is hard to distinguish by routine staining.
Developmental stage of oocytes was determined
according to King .
RESULTS AND DISCUSSION
As chromocenter mutations phenotypically express
themselves in both meiosis and mitosis [5–7], I studied
the structure of chromocenter not only in oocytes, but
also in somatic follicle cells that form the envelope of
egg chambers. In the dividing follicle cells of early egg
chambers, I distinguished the stages of interphase,
prophase, and prometaphase. In addition, I studied the
nondividing endoreplicating polyploid nuclei of folli-
cle cells in late egg chambers.
In nuclei, I considered the number of groups of hetero-
chromatin bands (HBs). The intensity and color of HBs
differed from those of euchromatin regions (Figs. 1a, 1b).
In somatic cells, I observed 1 to 16 HBs at inter-
phase (Figs. 1c–h). Sometimes, the nucleolus, which is
associated with the groups of HBs, was also stained
(Fig. 1d), as well as the associations between bands,
especially if two groups of HBS were found in the
nucleus (Figs. 1f, 1g). The distribution of the number of
nuclei by the number of groups of HBs in follicle cells
of (+/+) the wild and (
) mutant lines is shown
in Fig. 2a. In both wild-type females and female
homozygous for mutation
, most of nuclei con-
tained two groups of HBs; a smaller number of nuclei
Genetic Control of the Formation and Reorganization
of Chromocenter in
V. L. Chubykin
Institute of Cytology and Genetics, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Received February 19, 2001
—The chromocenter integrates the entire
genome into a unit. The formation and reorga-
nization of chromocenter are genetically determined. Currently, several mutations affecting the structure of
chromocenter have been described. In this work, I present evidence on the time of the formation and reorgani-
zation of chromocenter in mitotic and meiotic cells of females of the wild type and the
mutant line obtained
by selection of mosaic clones produced from mitotic recombination of chromosomes in the dividing embryo
cells. In females homozygous for this mutation, the second stage of the formation of chromocenter (joining two
groups of nonhomologous chromosomes X-4 and 2-3 into a united ring structure =X=2=3=4=) is disturbed. The
differences between the mitotic and meiotic reorganization of chromocenter and the role of chromocenter in the
control of chromosome segregation are discussed.