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1.
A new murine tester stock for primary nondisjunction incorporates three genetically marked Robertsonian translocations with tribrachial homology (TBH): Rb(6.15)1Ald, Rb(4.6)2Bnr, and Rb(4.15)4Rma. The resultant tricentromeric meiotic configuration leads to 100% aneuploid gametes, but the TBH stock can be maintained by intercrossing, through the complementation of nullisomic and disomic gametes. The only neonatal survivors from tescrosses to wild type come from complementation of aneuploid gametes and genetic tests allow wild type gains or losses of Chromosomes 4, 6, and 15 to be distinguished. Alternatively, cytogenetic examination allows products of wild type chromosome gain, with one metacentric, to be separated from chromosome loss with two metacentrics. A pilot study, with 0-2 Gy X-irradiation of oocytes at diakinesis, revealed twelve examples of chromosome loss in wild type gametes but none of chromosome gain and thus provided no evidence for the induction of nondisjunction. 相似文献
2.
Two new genetic methods for detecting autosomal non-disjunction and chromosome loss in mice are described. Both methods involve the use of marker genes and Robertsonian translocations, the latter present only in tester parents, to detect events in chromosomally normal mice. With the Rb method, the tester parent carries one or more Robertsonian translocations heterozygously; with the MBH method the tester parent carries two Robertsonian translocations showing monobrachial homology. The high rates of meiotic non-disjunction in the tester mice provide gametes with specific extra or missing chromosomes which, at fertilization, can allow the survival of a proportion of the zygotes lacking or carrying an extra specific chromosome from tested chromosomally normal parents. The Rb method has been assessed for X-ray-induced chromosome 1 loss and non-disjunction in mature oocytes and also for such chromosome 1 loss from the maternal pronuclei of 1-cell zygotes. The MBH method has been assessed for X-ray-induced chromosome 1 loss in male postmeiotic cells and for non-disjunction in spermatocytes. Both methods proved effective in detecting chromosome 1 loss. A single case of the much rarer non-disjunctional event was also found. As applied, both methods compared favourably with the numerical sex chromosome anomaly (NSA) method and have considerable potential for further development. 相似文献
3.
Sonta S 《Mutation research》2002,504(1-2):193-202
Using 14 Chinese hamster stocks with various reciprocal translocations, chromosomally unbalanced gametes were produced and used to investigate the participation of the unbalanced gametes in fertilization and the development of unbalanced embryos. The selection of chromosomally abnormal gametes during fertilization was investigated by the chromosomal analysis of meiotic cells in heterozygotes for the 14 reciprocal translocations and pronuclei of fertilized ova obtained from crossing these heterozygotes. Compared with the expected frequencies from meiotic metaphase II (MII) scoring, the frequencies of male pronuclei having commonly a deficiency of chromosome 1 (q14-->q42) or chromosome 3 (p23-->q31) in one-cell embryos decreased significantly. However, the frequencies of male pronuclei with other abnormalities were all consistent with those expected from MII scoring. In contrast, the frequencies of female pronuclei with any karyotype including the same ones, as those decreased in male pronuclei from the translocation heterozygotes were all consistent with those estimated from MII scoring. These results suggest that gametes with nullisomies as well as disomies for any chromosomal segments may mostly participate in fertilization, whereas some sperm nullisomic for the specific segments of chromosomes 1 and 3 may fail to fertilize. On the other hand, the zygotic selection of chromosomal imbalance was investigated by direct analyses of pre-implantation embryos from crosses between chromosomally normal females and male heterozygotes from the 14 stocks with various reciprocal translocations. The chromosomal and morphological analysis revealed that some embryos were arrested in development at the two-cell stage and their common abnormality was partial monosomy for chromosome 1 or 2. Embryos with partial monosomy including chromosomes 1, 3 and 4 showed arrested development at four-eight-cell stages. Among day 4 embryos, some chromosomally unbalanced embryos, mainly with a deficiency of other segments, such as chromosomes 1p, 2q, 5q and 8, had fewer blastomeres than karyotypically normal and balanced embryos. The homology between the mouse and the Chinese hamster chromosomes relating to the developmental abnormalities at early stages was partially confirmed. 相似文献
4.
Sonta S 《Cytogenetic and genome research》2004,104(1-4):261-270
Chinese hamster stocks with various structurally abnormal chromosomes have been produced by X irradiation. Among these stocks, 18 with various reciprocal translocations were used to investigate the participation of unbalanced gametes in fertilization and the development of unbalanced embryos. Among males as well as females heterozygous for the same translocation, there is no difference in the frequency of each disjunctional class. The participation of chromosomally unbalanced gametes in fertilization was investigated by chromosomal analysis of meiotic cells in heterozygotes for the 18 reciprocal translocations and pronuclei of fertilized ova obtained from crossing these heterozygotes. Compared with the expected frequencies from MII scoring, the frequencies of male pronuclei having a common deficiency of chromosome 1 (1q17-->1q42) or chromosome 3 (3p23-->3q31) decreased significantly in one-cell embryos. However, the frequencies of male pronuclei with other abnormalities were all consistent with those expected from MII scoring. In contrast, the frequencies of female pronuclei with any karyotype including the same abnormalities as those decreased in male pronuclei from the translocation heterozygotes were all consistent with those estimated from MII scoring. These results revealed clearly that most gametes with nullisomies as well as disomies for any chromosomal segments may participate in fertilization, whereas only male gametes nullisomic for certain segments of chromosomes 1 and 3 failed to participate in fertilization. The zygotic selection of chromosomal imbalance was also investigated by direct chromosomal and morphological analyses of preimplantation embryos from crosses between karyotypically normal females and male heterozygotes from the 18 stocks with various reciprocal translocations. These analyses revealed that some embryos were arrested in development at the two-cell stage. The karyotype of these two-cell embryos had a common deficiency in a segment of chromosome 1 or chromosome 2. Embryos with partial monosomy including chromosomes 1, 3, 4 and 5 showed arrested development at four- to eight-cell stages. Among day 4 embryos, some chromosomally unbalanced embryos, mainly with a deficiency of segments of chromosomes 1p, 1q, 2q, 5q, 7q and 8, had fewer blastomeres than karyotypically normal and balanced embryos. The homology between Chinese hamster and mouse chromosomes relating to abnormal embryogenesis at early stages has been partially confirmed from reported maps of chromosomes. The Chinese hamster is useful for further cytogenetic studies during the stages of meiosis and early embryogenesis. 相似文献
5.
In this report some data concerning the male meiotic system of mice heterozygous for Rb(11.13)4Bnr are presented and compared with those of a chromosomally normal Swiss random-bred stock. Change of the genetic background from a C3H/Swiss hybrid situation to the fourth backcross generation (to the Swiss random-bred stock), did not alter the average frequency of aneuploid secondary spermatocytes. This was confirmed by studies on post-implantation loss. Spermatogenic characteristics of Rb4/+ mice, such as testis weight, sperm production and the number of diplotene-metaphase-I figures found in stage XII of the seminiferous epithelium, suggest delay and cell death during this period. These data support our working hypothesis that such an aberrant chromosome system may be more prone to radiation effects and therefore is promising in our cytological studies into the causes of spontaneous and in our cytological studies into the causes of spontaneous and induced autosomal non-disjunction during meiosis in the mouse. 相似文献
6.
Is there selection against aneuploid sperm during spermatogenesis and fertilization? To address this question, we used male mice doubly heterozygous for the Robertsonian (Rb) translocations Rb(6. 16)24Lub and Rb(16.17)7Bnr, which produce high levels of sperm aneuploid for chromosome 16, the mouse counterpart of human chromosome 21. The frequencies of aneuploid male gametes before and after fertilization were compared by analyzing approximately 500 meiosis II spermatocytes and approximately 500 first-cleavage zygotes using fluorescence in situ hybridization with a DNA painting probe mixture containing three biotin-labeled probes specific for chromosomes 8, 16, and 17 plus a digoxigenin-labeled probe specific for chromosome Y. Hyperhaploidy for chromosome 16 occurred in 20.0% of spermatocytes and in 21.8% of zygotes. Hypohaploidy for chromosome 16 occurred in 17.0% and 16.7% of spermatocytes and zygotes, respectively. In addition, there was no preferential association between chromosome 16 aneuploidy and either of the sex chromosomes, nor was there an elevation in aneuploidy for chromosomes not involved in the Rb translocations. These findings provide direct evidence that there is no selection against aneuploid sperm during spermiogenesis, fertilization, and the first cell cycle of zygotic development. 相似文献
7.
The selection of chromosomally abnormal gametes was investigated in the Chinese hamster by direct chromosome analysis of meiotic cells and one-cell embryos obtained from crossing heterozygotes for two reciprocal translocations, T(1;3)7Idr and T(1;3)8Idr. Expected frequencies of male and female gametes with different chromosome constitutions were estimated by scoring of secondary meiotic metaphase (MII) cells in the translocation heterozygotes. The frequency of gametes with each karyotype that participated in fertilization was investigated in pronuclei from translocation heterozygotes in one-cell embryos obtained from crossing the heterozygotes with karyo-typically normal animals. Compared with the expected frequencies from MII scoring, the frequencies of male pronuclei having some karyotypes in one-cell embryos decreased significantly. The karyotypes of male pronuclei showing a decreased frequency were commonly characterized by a deficiency of the long-arm segment of chromosome 1 (q13----qter) or by a deficiency of almost the whole arms of chromosome 3. On the other hand, the frequencies of female pronuclei with the same karyotypes were all consistent with those estimated from MII scoring. These results suggest that sperm nullisomic for certain segments of some chromosomes may fail to participate in fertilization. 相似文献
8.
Common shrews display two types of Robertsonian (Rb) heterozygosity: simple (where CIII configurations are formed at meiosis
I) and complex (which have longer meiotic chains or rings). Based on an analysis of large sample sizes (over 100) of MII cells
per specimen, we estimated the non-disjunction frequency in seven Rb homozygotes and 21 complex Rb heterozygotes (CIV and
CV) of Sorex araneus Linnaeus, 1758. The analysis showed high betweenindividual variability. The mean level of non-disjunction in homozygotes
(2.01%) was significantly lower than in CIV and CV heterozygotes (4.27% and 5.78%, respectively). The study demonstrated that
non-disjunction frequency in male CIV and CV heterozygotes was similar to that in simple heterozygotes in the common shrew. 相似文献
9.
Frequency and distribution of aneuploidy in human female gametes 总被引:15,自引:2,他引:13
Franck Pellestor 《Human genetics》1991,86(3):283-288
Summary During the past 6 years, 14 cytogenetic studies on human oocytes recovered during in vitro fertilization procedures have been published; they report contradictory results. The present survey has pooled the more than 1500 oocyte chromosome complements examined to date, in order to determine generalized trends in chromosomal abnormalities of female gametes. The overall frequency of abnormalities in mature oocytes is 24.0% with a large majority of aneuploidies (22.8%) over structural aberrations (1.2%), which could be explained by the difficulty in the detection of structural abnormalities in oocyte chromosome sets. An analysis of the distribution of non-disjunction among all chromosomes was also performed. In the A, C, D, and especially in the G groups, there is a significant difference between the observed non-disjunction and the frequencies expected from an equal partitioning of non-disjunction among all chromosomes. These data are discussed with reference to the differences obtained from cytogenetic studies on human sperm and from investigations on spontaneous abortion. 相似文献
10.
A detailed analysis was made of the chromosomes in 1008 M II figures from three different types of heterozygous Robertsonian translocation-carrying rams (53,xy,t1; 53,xy,t3) and 225 M II figures from homozygous Robertsonian translocation-carrying rams (52,xy,t1t1; 52,xy,t3t3) and rams of normal karotype (54,xy). No hypermodal cells were recorded in either the normal or the homozygous rams, but from 4-5% to 9-2% of M II cells from the heterozygous rams were hypermodal. The heterozygous rams also produced a significantly higher level of hypomodal cells suggesting that, in addition to non-disjunction, lagging at anaphase I may have occurred. There were also distinct differences in M II aneuploid spermatocyte frequency between heterozygous versus normal and homozygous rams. Fewer balanced translocation X-carrying M II cells were recorded than expected in three of the four 53,xy,t2 rams. This coincides with mating data which suggest that 26,x,t2 gametes may occur less frequently than expected. Since ewes of normal karotype mated to 53,xy,t rams conceive to first service at a rate equal to or better than normal mating groups, and because no blastocysts with unbalanced karotypes associated with the t1 translocation have been recorded, it is suggested that only euploid spermatozoa are involved in fertilization. In the sheep, aneuploid spermatocytes probably degenerate before sperm maturation. 相似文献
11.
Leonore Dennhöfer 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1975,45(6):250-253
Summary The present paper deals with crossing experiments on translocation heterozygotes in the mosquitoCulex pipiens L. It is shown that the ratio of euploid and aneuploid gametes is determined by two allelomorphs of one single inheritable factor. These experiments agree with our hypothesis that the ratio of segregation types in a translocation heterozygous organism (alternate and adjacent) is determined by a series of multiple alleles of a single mendelian factor.The investigations were done in the Department of Biology (21) of the Johannes Gutenberg-University in Mainz. 相似文献
12.
A Robertsonian translocation in the mouse between the X chromosome and chromosome 2 is described. The male and female carriers of the Rb(X.2)2Ad were fertile. A homozygous/hemizygous line was maintained. The influence of the X-autosomal Robertsonian translocation on anaphase I non-disjunction in male mice was studied by chromosome counts in cells at metaphase II of meiosis and by assessment of aneuploid progeny. The results conclusively show that the inclusion of Rb2Ad in the male genome induces non-disjunction at the first meoitic division. In second metaphase cells the frequency of sex-chromosomal aneuploidy was 10.8%, and secondary spermatocytes containing two or no sex chromosome were equally frequent. The Rb2Ad males sired 3.9% sex-chromosome aneuploid progeny. The difference in aneuploidy frequencies in the germ cells and among the progeny suggests that the viability of XO and XXY individuals is reduced. The pairing configurations of chromosomes 2, Rb2Ad and Y were studied during meiotic prophase by light and electron microscopy. Trivalent pairing was seen in all well spread nuclei. Complete pairing of the acrocentric autosome 2 with the corresponding segment of the Rb2Ad chromosome was only seen in 3.2% of the cells analysed in the electron microscope. The pairing between the X and Y chromosome in the Rb2Ad males corresponded to that in males with normal karyotype. Reasons for sex-chromosomal non-disjunction despite the normal pairing pattern between the sex chromosomes may be seen in the terminal chiasma location coupled with the asynchronous separation of the sex chromosomes and the autosomes.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
13.
Sarah Cohen 《Journal of experimental marine biology and ecology》1990,140(3):147-158
Self-compatible gametes and short-lived larvae in the sessile solitary ascidians Corella inflata Huntsman and Chelyosoma productum Stimpson suggest that field populations might be characterized by limited dispersal and self-fertilization. Because C. inflata in the laboratory spawns gametes into its atrium and retains offspring until they are competent to settle, it was expected to show an almost complete lack of outcrossing in the field. C. productum, in the laboratory, spawns streams of gametes, sometimes eggs and sperm simultaneously, into the water and is self-compatible. Embryos develop for an additional day in the plankton before hatching. Thus, some setting was also expected for C. productum, though it appears to have a far greater potential for gene flow with both outcrossing and more extended larval dispersal possible. Genetic population structure in these species was examined using protein electrophoresis to determine frequencies of heterozygotes at the polymorphic locus glucosephosphate isomerase (GPI). Heterozygotes were found in both species indicating that outcrossing occurs. At three locations, C. inflata genotype frequencies did not differ significantly from Hardy-Weinberg expected frequencies and indicated from 41 to 100% outcrossing. Another measure of breeding system (S), calculated from the same data, gave a pooled location outcrossing estimate of 82%. Also, the three locations did not differ significantly from each other in allele frequencies, indicating a lack of genetic differentiation on a scale ≈ 100 km. Brooded embryos and short-lived larvae do not appear to be limiting gene flow on this scale in this species. 相似文献
14.
Summary Chromosomal analysis of 100 second metaphases from 19 men attending an infertility clinic for various reasons was carried out to estimate the rate of non-disjunction occurring at first meiotic division. Second metaphases were selected on the basis of the good spread of their chromosomes. Karyotypes were performed using the relative length of the chromosomes and the centromeric index. Among aneuploid cells, only those containing a hyperhaploid complement (24) were regarded as informative. Of the 100 MII cells, two were hyperhaploid. The frequency of aneuploid MII cells following non-disjunction at first meiotic division is compared to the rate of aneuploid spermatozoa observed after using fertilization of zona-free golden hamster eggs. 相似文献
15.
G. G. Doyle 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,72(6):799-806
Summary Almost all autotetraploids produce aneuploid progeny because of irregularities at meiosis. Aneuploid plants produce high frequencies of aneuploids. If it were not for selection against aneuploid gametes and sporophytes the amount of aneuploidy would increase every generation. Most experimental and theoretical studies on population genetics and heterosis in autotetraploids have neglected aneuploidy as a factor. To take aneuploidy into account experimentally requires the cytological identification of all chromosomes and to consider it theoretically requires a huge amount of computations. Consequently, microcomputer programs have been devised to show the effects of random mating and self-fertilization in autotetraploid populations. According to the model aneuploidy rapidly increases in randomly mated and self-fertilized autotetraploid populations until they achieve an equilibrium where the amount of aneuploidy introduced into the population is balanced by the amount of aneuploidy removed from the population by selection. The model suggests that self-fertilized populations have greater frequencies of aneuploid gametes and zygotes than do randomly mated populations and therefore aneuploidy may be a significant cause of the great inbreeding depressions found in autotetraploids.Contribution from the Missouri Agricultural Experiment Station. Journal Series No. 9998 相似文献
16.
Daniel K Lange J Hached K Fu J Anastassiadis K Roig I Cooke HJ Stewart AF Wassmann K Jasin M Keeney S Tóth A 《Nature cell biology》2011,13(5):599-610
Meiotic crossover formation between homologous chromosomes (homologues) entails DNA double-strand break (DSB) formation, homology search using DSB ends, and synaptonemal-complex formation coupled with DSB repair. Meiotic progression must be prevented until DSB repair and homologue alignment are completed, to avoid the formation of aneuploid gametes. Here we show that mouse HORMAD1 ensures that sufficient numbers of processed DSBs are available for successful homology search. HORMAD1 is needed for normal synaptonemal-complex formation and for the efficient recruitment of ATR checkpoint kinase activity to unsynapsed chromatin. The latter phenomenon was proposed to be important in meiotic prophase checkpoints in both sexes. Consistent with this hypothesis, HORMAD1 is essential for the elimination of synaptonemal-complex-defective oocytes. Synaptonemal-complex formation results in HORMAD1 depletion from chromosome axes. Thus, we propose that the synaptonemal complex and HORMAD1 are key components of a negative feedback loop that coordinates meiotic progression with homologue alignment: HORMAD1 promotes homologue alignment and synaptonemal-complex formation, and synaptonemal complexes downregulate HORMAD1 function, thereby permitting progression past meiotic prophase checkpoints. 相似文献
17.
We analysed polymorphism for pericentric inversion in chromosome 3 of Oligoryzomys nigripes (Rodentia: Sigmodontinae) in several populations in Brazil and examined the meiotic behaviour of this chromosome in heterozygotes. We observed an orderly pairing of all chromosomes at pachytene in heterozygotes for the inverted chromosome 3. No indication of meiotic arrest and germ-cell death was found. Electron microscopy of synaptonemal complexes and conventional meiotic analysis indicated strictly nonhomologous synapsis and crossing-over suppression in the inverted region in the heterozygotes, which prevent the formation of unbalanced gametes. Thus, the pericentric inversion in chromosome 3 does not apparently result in any selective disadvantages in heterozygous carriers. In the majority of the populations studied, the frequencies of acrocentric homozygotes, metacentric homozygotes, and heterozygotes were in Hardy-Weinberg equilibrium. However, in some populations, we detected an excess of heterozygotes and a deficiency of acrocentric homozygotes. 相似文献
18.
C. L. O’Keefe D. K. Griffin Christopher J. Bean A. Gregory Matera T. J. Hassold 《Human genetics》1997,101(1):61-66
Over the past few years, several groups have used fluorescence in situ hybridization (FISH) to study aneuploidy in human
sperm. Several important observations have derived from these studies, including the demonstration of chromosome-specific
variation in non-disjunction frequencies, and the possible association of aneuploidy with environmental agents and with increasing
paternal age. However, an important technical limitation of these studies has been the inability to distinguish between autosomal
non-disjunction occurring at meiosis I and meiosis II. In the present report, we describe a simple FISH-based approach designed
to overcome this limitation. Using oligonucleotide probes capable of distinguishing subtle differences in the alpha satellite
sequences of chromosome 17, we demonstrate that (in appropriate heterozygotes) it is possible to simultaneously identify disomic
sperm and to determine the meiotic stage of origin of the additional chromosome. This novel approach has important implications
for future FISH sperm studies, since the ability to distinguish between meiosis I and meiosis II non-disjunction will make
it possible to determine whether putative etiological agents affect chromosome segregation at both, or only one, of the two
meiotic stages.
Received: 19 March 1997 / Accepted: 12 June 1997 相似文献
19.
A variation of the mouse spot test is described that is designed to distinguish between spots of altered coat colour that arise by reciprocal mitotic recombination and those caused by somatic mutation or non-disjunction. Mouse fetuses that were heterozygous for two, linked coat colour genes were irradiated (1.5 Gy X-rays) in utero at 10.25-10.50 days post coitum (p.c.) or left untreated. Subsequently, the coats were classified for the presence of spots of altered colour. The irradiated embryos were heterozygous for the linked genes pink-eyed dilution (p) and albino (c) and were produced by both the repulsion and coupling crosses. Half of the reciprocal recombination events between the centromere and the proximal marker (p), in heterozygotes with p and c in repulsion, should produce twin spots. No such twin spots would be expected from a similar event in the coupling heterozygotes. The coats of 238 irradiated and 208 untreated repulsion heterozygotes plus 107 irradiated and 314 untreated coupling heterozygotes were classified for spots. One irradiated, repulsion heterozygote had a diffuse twin spot that was only recognisable by microscopic examination of the hairs. We conclude that if the treatment described induces mitotic recombination in the mouse, it does so with low efficiency. 相似文献
20.
During meiosis, DNA replication is followed by two successive rounds of chromosome segregation (meiosis I and II), which give rise to genetically diverse haploid gametes. The prophase of the first meiotic division is highly regulated and alignment and synapsis of the homologous chromosomes during this stage are mediated by the synaptonemal complex. Incorrect assembly of the synaptonemal complex results in cell death, impaired meiotic recombination and aneuploidy. Oocytes with meiotic defects often survive the first meiotic prophase and give rise to aneuploid gametes. Similarly affected spermatocytes, on the other hand, almost always undergo apoptosis at a male-specific meiotic checkpoint, located specifically at epithelial stage IV during spermatogenesis. Many examples of this stage IV-specific arrest have been described for several genetic mouse models in which DNA repair or meiotic recombination are abrogated. Interestingly, in C. elegans, meiotic recombination and synapsis are monitored by two separate checkpoint pathways. Therefore we studied spermatogenesis in several knockout mice (Sycp1(-/-), Sycp3(-/-), Smc1beta(-/-) and Sycp3/Sycp1 and Sycp3/Smc1beta double-knockouts) that are specifically defective in meiotic pairing and synapsis. Like for recombination defects, we found that all these genotypes also specifically arrest at epithelial stage IV. It seems that the epithelial stage IV checkpoint eliminates spermatocytes that fail a certain quality check, being either synapsis or DNA damage related. 相似文献