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1.
Studies of the meiotic distribution of compound-3 chromosomes in males and females of Drosophila melanogaster provided the following results. (1) From females homozygous for the standard arrangement of all chromosomes other than C(3L) and C(3R), less than 5% of the gametes recovered were nullosomic or disomic for compound-3 chromosomes. The frequency of nonsegregation differed between strains, but within a given strain it remained relatively constant. (2) According to egg-hatch frequencies, C(3L) and C(3R) segregate independently during spermatogenesis. (3) In females, structurally heterozygous second chromosomes occasion a marked increase in the recovery of nonsegregational progeny; in males, rearranged seconds have no apparent influence on the distribution of compound thirds. (4) The highest frequencies of nonsegregational progeny were recovered from C(3L);C(3R) females carrying compound-X (plus free Y) chromosomes. (5) In comparing the recovery of nonsegregating compound thirds to the recovery of rearranged heterologs, a definite nonrandom distribution was realized in several crosses. These results are examined in reference to the concepts of distributive pairing (Grell 1962). Moreover, considering the structural nature of compound autosomes, we propose that nonhomologous (distributive) pairing is a property of the centromeric region and suggest that rearrangements involving breaks in this region possibly alter the effectiveness of distributive pairing forces. 相似文献
2.
Meiosis in Male DROSOPHILA MELANOGASTER. II. Nonrandom Segregation of Compound-Second Chromosomes
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Richard C. Gethmann 《Genetics》1976,83(4):743-751
The segregation of compound-second chromosomes in males from two different stocks has been examined. Segregation is random in males from the C(2L)RM4, dp; C(2R)RM4, px stock. Gametes containing only one of the two compound chromosomes comprise 50% of the gametes, and gametes containing either both elements or neither element make up the other 50% of the gametes.——In males from the C(2L)RM, b; C(2R)RM, cn stock, gametes containing either C(2L)RM, b or C(2R)RM, cn make up the majority of the gametes. Gametes containing both chromosomes or neither chromosome account for only 2-3% of the gametes. The nonrandom segregation is due to the C(2R)RM, cn chromosome.——Viability is reduced in flies carrying the C(2R)RM, cn chromosome. This includes larval lethality, delayed development and premature adult lethality. Cytologically, this chromosome contains a large duplication of 2L material, which includes material proximal to region 38 or 39. It is suggested that the viability and segregational properties associated with this chromosome are due to the duplicated 2L material. 相似文献
3.
Meiotic Behavior of Compound Autosomes in Females of DROSOPHILA MELANOGASTER: Interchromosomal Effects and the Source of Spontaneous Nonsegregation
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In females of Drosophila melanogaster, compound autosomes enter the repulsion phase of meiosis uncommitted to a particular segregation pattern because their centromeres are not restricted to a bivalent pairing complex as a consequence of crossing over. Their distribution at anaphase, therefore, is determined by some meiotic property other than exchange pairing, a property that for many years has been associated with the concept of nonhomologous pairing. In the absence of heterologous rearrangements or a free Y chromosome, C(3L) and C(3R) are usually recovered in separate gametes, that is as products of meiotic segregation. Nevertheless, there is a regular, albeit infrequent, recovery of reciprocal meiotic products (the nonsegregational products) that are disomic and nullosomic for compound thirds. The frequency of these exceptions, which is normally between 0.5 and 5.0%, differs for the various strains examined, but remains constant for any given strain. Since previous studies have not uncovered a cause for this base level of nonsegregation, it has been referred to as the spontaneous frequency. In this study, crosses between males and females whose X chromosomes, as well as compound autosomes, are differentially marked reveal a highly significant positive correlation between the frequency of compound-autosome nonsegregation and the frequency of X-chromosome nondisjunction. However, an inverse correlation is found when the frequency of nondisjunction is related to the frequency of crossing over in the proximal region of the X chromosome. These findings have been examined with reference to the distributive pairing and the chromocentral models and interpreted as demonstrating (1) that nonsegregational meiotic events arise primarily as a result of nonhomologous interactions, (2) that forces responsible for the segregation of nonhomologous chromosomes are properties of the chromocentral region, and (3) that these forces come into expression after the exchange processes are complete. 相似文献
4.
V. L. Chubykin 《Russian Journal of Genetics》2009,45(9):1027-1039
Data are presented in favor of universal significance of physical connections between pericentromeric regions of homologs
in their orientation to the opposite poles of the first meiotic division in Drosophila melanogaster. Disturbances in the formation of such connections caused by structural or locus mutations are compensated for by the presence
of pericentromeric chiasmata between homologs or (in the case of their absence) by chromocentral connections between nonhomologs
being preserved up to the prometaphase. In the latter case, an interchromosome effect on chromosome disjunction and nonhomologous
pairing is registered by genetic methods. Inhibition of the formation of the division spindle fibers during prometaphase of
meiosis 1 by the long-term action of colcemide promotes the retention of connections between paired nonexchanged homologs
and between nonhomologous chromosomes with abnormal homologous pairing because of heterozygosity for numerous inversions and
transpositions (X and autosome 2). These connections are registered cytologically. Cytologically registered are also connections
between normal X chromosomes and metacentric compounds by the arms of autosome 2 (C(2L)RM, C(2R)RM), which is the known case
of the interchromosome effect on chromosome nondisjunction. It is supposed that cytologically detected associations between
compounds are realized through a normal mechanism, as a result of interaction and formation of orienting connections between
the homologous pericentromeric regions of these compounds. Cytological evidence is presented for colocation of compounds in
the chromocentrally organized nucleus of somatic and germline cells. 相似文献
5.
P. Portin 《Genetica》1992,85(2):139-145
Heterologous segregation of the Y chromosome and secondary non-disjunction of the X chromosomes in female meiosis of Drosophila melanogaster was investigated in ten different crosses where different constellations of translocation/inversion or translocation/translocation systems of the large autosomes were present in the female parent. It appeared that the Y chromosome always segregates from the shortest of the possible heterologous pairing partners. This may be due to size-dependent mechanism of so-called distributive disjunction or to the possibility that the shorter the chromosome element is, the more easily it moves in the nucleus of the oocyte. Secondary non-disjunction of the X chromosomes appeared to be lower the more possible autosomal pairing partners the Y chromosome had, suggesting that the autosomes effectively compete with the X chromosomes for pairing with the Y chromosome. An alternative explanation is that, due to interchromosomal effect on recombination, crossing over in the X chromosomes was different in different experiments. 相似文献
6.
Meiotic behaviour of sex chromosomes investigated by three-colour FISH on 35 142 sperm nuclei from two 47,XYY males 总被引:5,自引:0,他引:5
E. Chevret S. Rousseaux M. Monteil Y. Usson J. Cozzi R. Pelletier B. Sèle 《Human genetics》1997,99(3):407-412
Meiotic segregation of sex chromosomes from two fertile 47,XYY men was analysed by a three-colour fluorescence in situ hybridisation
procedure. This method allows the identification of hyperhaploidies (spermatozoa with 24 chromosomes) and diploidies (spermatozoa
with 46 chromosomes), and their meiotic origin (meiosis I or II). Alpha-satellite probes specific for chromosomes X, Y and
1 were observed simultaneously in 35 142 sperm nuclei. For both 47,XYY men (24 315 sperm nuclei analysed from one male and
10 827 from the other one) the sex ratio differs from the expected 1:1 ratio (P < 0.001). The rates of disomic Y, diploid YY and diploid XY spermatozoa were increased for both 47,XYY men compared with
control sperm (142 050 sperm nuclei analysed from five control men), whereas the rates of hyperhaploidy XY, disomy X and disomy
1 were not significantly different from those of control sperm. These results support the hypothesis that the extra Y chromosome
is lost before meiosis with a proliferative advantage of the resulting 46,XY germ cells. Our observations also suggest that
a few primary spermatocytes with two Y chromosomes are able to progress through meiosis and to produce Y-bearing sperm cells.
A theoretical pairing of the three gonosomes in primary spermatocytes with an extra sex chromosome, compatible with active
spermatogenesis, is proposed.
Received: 12 April 1996 / Revised: 26 August 1996 相似文献
7.
O. G. Silkova O. B. Dobrovolskaya A. I. Shchapova V. K. Shumny 《Russian Journal of Genetics》2009,45(9):1062-1066
Regulation of meiotic restitution in androgenic haploids generated by cultivation of isolated anthers of three wheat-rye substitution
lines 2R(2D)1, 2R(2D)3, and 6R(6A) (Triticum aestivum L., cultivar Saratovskaya 29/Secale cereale L., cultivar Onokhoiskaya) was studied. The presence of rye chromosomes and the absence of homeologous wheat chromosomes
in the haploid plant genome was shown to cause meiotic restitution, as observed in the case of androgenic haploids 6R(6A),
or to inhibit it—in meiosis of haploids 2R(2D)1 and 2R(2D)3. In haploids of lines 2R(2D)1 and 2R(2D)3, the reductional type of division of univalent chromosomes was observed, leading to preferential formation of tetrads. In
haploids of line 6R(6A), the equational type of division of univalents into sister chromatids, resulting in the block of the
second division and formation of diads in approximately 50% of cells, was detected. These results confirm data on the effect
of the genotype of line 2R(2D)1 on the induction of reductional type division of univalents and two-phase meiosis, which were earlier obtained in studies
of meiosis in polyhaploids 2R(2D)1 × S. cereale L., cultivar Onokhoiskaya. 相似文献
8.
G. M. Evans E. W. Davies 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,71(2):185-192
Summary The degree of preferential pairing of homologous chromosomes was estimated in a series of tetraploid hybrids of Lolium temulentum x Lolium perenne by means of cytological and genetic analyses. The correlations between the frequency of bivalents at first metaphase of meiosis in the hybrid tetraploids and the degree of preferential pairing calculated from the segregation pattern of isozyme alleles in a test cross was extremely high. The results showed clearly that suppression of heterogenetic pairing in these Lolium tetraploids is achieved by a genetic system involving the A chromosomes as well as the B chromosome system which has been known for some time. Certain similarities with the genetic system controlling pairing in polyploid wheats are discussed. 相似文献
9.
The effect of B chromosomes on chromosome pairing at meiosis was investigated in the species hybrid Lolium temulentum x L. perenne at both the diploid and tetraploid level. The presence of B chromosomes drastically reduced association of homoeologous chromosomes in both the diploids and tetraploids. This was evident from the high frequency of univalents recorded in PMC's of diploid hybrids with B's and from the predominantly bivalent association of homologous chromosomes in tetraploids of this type. In the absence of B's homoeologous pairing was extensive giving a high frequency of bivalents in the diploids and multivalents as well as bivalents and univalents in the tetraploids. 相似文献
10.
Triploidy has generally been considered to be an evolutionary dead end due to problems of chromosomal pairing and segregation
during meiosis. Thus, the formation of tetraploids and diploids from triploid types is a rare phenomenon. In the present study,
we demonstrated that inbreeding of the triploid planarian Dugesia ryukyuensis resulted in both diploid and triploid offspring in nature. In the triploids of D. ryukyuensis, chiasmata between homologous chromosomes were observed in both female and male germ lines. This result suggests that both
diploid and triploid offspring of this species are produced bisexually by zygotic fusion between sperm and eggs. Hence, this
phenomenon may be a novel mechanism in planarian for escaping the triploid state. 相似文献
11.
Summary A Neurospora crassa mutation, mei-2, affecting meiosis and mutagen sensitivity, was characterized for its effect on meiotic recombination and chromosome pairing. Results from homozygous mei-2 crosses involving distant markers on the same chromosome demonstrated a drastic reduction in meiotic recombination. However, mitotic recombination continued to occur. Cytological observations indicated that pairing of homologous chromosomes in zygotene was greatly reduced or absent, resulting in aberrant segregation at anaphase I and often at subsequent divisions as well. The few mature ascospores produced were frequently disomic for one or more chromosomes. 相似文献
12.
Regional Bivalent-Univalent Pairing versus Trivalent Pairing of a Trisomic Chromosome in Saccharomyces Cerevisiae 总被引:1,自引:0,他引:1
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In meiosis I, homologous chromosomes pair, recombine and segregate to opposite poles. These events and subsequent meiosis II ensure that each of the four meiotic products has one complete set of chromosomes. In this study, the meiotic pairing and segregation of a trisomic chromosome in a diploid (2n + 1) yeast strain was examined. We find that trivalent pairing and segregation is the favored arrangement. However, insertions near the centromere in one of the trisomic chromosomes leads to preferential pairing and segregation of the ``like' centromeres of the remaining two chromosomes, suggesting that bivalent-univalent pairing and segregation is favored for this region. 相似文献
13.
Genetic dissection of heterochromatin in Drosophila: The role of basal X heterochromatin in meiotic sex chromosome behaviour 总被引:1,自引:1,他引:0
We have examined the female meiotic behaviour of three X chromosomes which have large deletions of the basal heterochromatin in Drosophila melanogaster. We find that most of this heterochromatin can be removed without substantially altering pairing and segregation of the two Xs. To compare the role of heterochromatin in male meiosis we have constructed individuals which carry two extra identical heterochromatic mini X chromosomes. These minis behave as univalents even though their heterochromatin is known to contain satellite DNA. We conclude therefore that this satellite DNA is not sufficient to allow effectively normal meiotic behaviour. In all other respects our results in the male extend and confirm Cooper's postulate that there exist specific pairing sites in the X heterochromatin. Thus we find no support in either female or male meiosis for the concept that satellite DNA is involved in meiotic chromosome pairing of either a chiasmate or an achiasmate kind. 相似文献
14.
Sharyn A. Endow 《Chromosoma》1992,102(1):1-8
Summary The recent finding that two proteins required for proper chromosome distribution in Drosophila oocytes are related to the microtubule motor protein, kinesin, provides new insights into the forces involved in meiotic chromosome movement. ncd is a spindle motor in meiosis but may perform a different role in the early mitotic divisions of the embryo. nod, until recently, has been thought to be a component of the distributive process of chromosome segregation. The finding that nod is a kinesin protein provides an alternative explanation of the effect of mutants on nonexchange chromosomes and suggests that nonexchange chromosomes segregate with exchange chromosomes in a single process, rather than via a two-step distributive system. 相似文献
15.
G. Jenkins 《Chromosoma》1986,93(5):413-419
Comparisons were made between two kinds of tetraploids derived from the hybrid Lolium temulentum x L. perenne. One hybrid behaves like an autotetraploid with multivalents at first metaphase of meiosis in pollen mother cells. The other behaves like an allotetraploid, in which pairing at first metaphase is restricted to bivalents comprised of strictly homologous chromosomes. The diploidisation of the latter form is controlled by determinants located on both the normal, A chromosomes and on supernumary B chromosomes. Reconstruction of synaptonemal complexes and their elements, from serial sections through pollen mother cell nuclei examined under the electron microscope, reveals that at zygotene pairing in both forms results in multivalent formation involving non-homologous as well as homologous chromosomes. The mechanism responsible for the diploidisation is, therefore, not based on a restriction of pairing at early meiosis to homologous chromosomes but on a correction or transformation of the multivalent chromosome associations to bivalents subsequent to zygotene. The transformation is not completed until late pachytene. In the multivalent-forming tetraploid a maximum of four chromosomes are associated at first metaphase. Yet configurations of a higher valency are found at zygotene. There is, therefore, a partial transformation of multivalents even in this autotetraploid form which restricts configurations at metaphase I to homologous and homoeologous chromosomes only. In both hybrids some homologous bivalents are not the product of resolution of multivalents but result from two-by-two pairing from the beginning of zygotene. 相似文献
16.
Emilie Knight Emma Greer Tracie Draeger Vera Thole Steve Reader Peter Shaw Graham Moore 《Functional & integrative genomics》2010,10(4):603-608
At the onset of meiosis, chromosomes first decondense and then condense as the process of recognition and intimate pairing
occurs between homologous chromosomes. We show here that okadaic acid, a drug known to induce chromosome condensation, can
be introduced into wheat interspecific hybrids prior to meiosis to induce chromosome pairing. This pairing occurs in the presence
of the Ph1 locus, which usually suppresses pairing of related chromosomes and which we show here delays condensation. Thus the timing
of chromosome condensation during the onset of meiosis is an important factor in controlling chromosome pairing. 相似文献
17.
P. M. Borodin E. A. Basheva F. N. Golenischev O. A. Dashkevich I. N. Kartavtseva A. P. Lisachov A. A. Torgasheva 《Paleontological Journal》2013,47(9):1035-1040
In many eutherian species, pairing and recombination of X and Y chromosomes are indispensable for normal meiotic progression and correct segregation of sex chromosomes. The rodent subfamily Arvicolinae provides an interesting exception. The majority of arvicoline species with asynaptic sex chromosomes belong to the genus Microtus sensu lato. However, some vole species of the genus Microtus and other genera display normal X-Y pairing in meiosis. These observations indicate that synaptic condition was typical for the common ancestor of all voles, but the gaps in taxonomic sampling makes impossible to identify a lineage or lineages, in which the asynapsis occurred. The methods of electron and fluorescent microscopy were used to study the synapsis of sex chromosomes in males of some additional species of the subfamily Arvicolinae. This extended taxonomic list allowed us to identify asynaptic species in every large lineage of the tribe Microtini. Apparently, the ability of sex chromosomes to pair and recombine in male meiosis was lost in arvicoline evolution for at least three times independently. Our results indirectly suggest the unnecessity of sex chromosome pairing in male meiosis of arvicoline rodents, and presence of alternate molecular mechanism of sex chromosome segregation in this large mammalian tribe. 相似文献
18.
Faridoon K. Yousafzai Nadia Al-Kaff Graham Moore 《Functional & integrative genomics》2010,10(2):157-166
During meiosis, chromosome numbers are halved, leading to haploid gametes, a process that is crucial for the maintenance of
a stable genome through successive generations. The process for the accurate segregation of the homologues starts in pre-meiosis
as each homologue is replicated and the respective products are held together as two sister chromatids via specific cohesion
proteins. At the start of meiosis, each chromosome must recognise its homologue from amongst all the chromosomes present in
the nucleus and then associate or pair with that homologue. This process of homologue recognition in meiosis is more complicated
in polyploids because of the greater number of related chromosomes. Despite the presence of these related chromosomes, for
polyploids such as wheat to produce viable gametes, they must behave as diploids during meiosis with only true homologues
pairing. In this review, the relationship between the Ph1 cyclin-dependent kinase (CDK)-like genes in wheat and the CDK2 genes in mammals and their involvement in controlling this
process at meiosis is examined. 相似文献
19.
《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2002,513(1-2):197-203
Centromere protein B (CENP-B) is a constitutive protein that binds to a highly conserved 17 bp motif located at most mammalian centromeres. To determine whether disruption of this gene affects chromosome segregation in male germ cells, we evaluated the frequencies of disomic and diploid sperm in CENP-B heterozygous and homozygous null mice using the mouse epididymal sperm aneuploidy (m-ESA) assay, a multicolor FISH method with probes for chromosomes X, Y and 8. The specificity and sensitivity of the m-ESA assay was demonstrated using Robertsonian (2.8) translocation heterozygotes as positive controls for sperm aneuploidy. Our results show that the frequencies of disomic and diploid sperm did not differ significantly between CENP-B heterozygous and homozygous null mice (P≥0.5) or from 129/Swiss isogenic mice (P≥0.5) and B6C3F1 mice (P≥0.2). These findings indicate that CENP-B does not have an essential role during chromosome segregation in male meiosis. 相似文献
20.
Zhiyun Gong Xiuxiu Liu Ding Tang Hengxiu Yu Chuandeng Yi Zhukuan Cheng Minghong Gu 《Chromosoma》2011,120(1):47-60
While many studies have provided significant insight into homolog pairing during meiosis, information on non-homologous pairing
is much less abundant. In the present study, fluorescence in situ hybridization (FISH) was used to investigate non-homologous pairing in haploid rice during meiosis. At pachytene, non-homologous
chromosomes paired and formed synaptonemal complexes. FISH analysis data indicated that chromosome pairing could be grouped
into three major types: (1) single chromosome paired fold-back as the univalent structure, (2) two non-homologous chromosomes
paired as the bivalent structure, and (3) three or more non-homologous chromosomes paired as the multivalent structure. In
the survey of 70 cells, 65 contained univalents, 45 contained bivalents, and 49 contained multivalent. Moreover, chromosomes
9 and 10 as well as chromosomes 11 and 12 formed non-homologous bivalents at a higher frequency than the other chromosomes.
However, chiasma was always detected in the bivalent only between chromosomes 11 and 12 at diakinesis or metaphase I, indicating
the pairing between these two chromosomes leads non-homologous recombination during meiosis. The synaptonemal complex formation
between non-homologs was further proved by immunodetection of RCE8, PAIR2, and ZEP1. Especially, ZEP1 only loaded onto the
paired chromosomes other than the un-paired chromosomes at pachytene in haploid. 相似文献