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PubMed1986

Mutagenicity testing of the pyrethroid insecticide cypermethrin in Drosophila.

The pyrethroid insecticide cypermethrin was tested for the induction of genetic damage in male germ cells of Drosophila melanogaster. Sex-linked recessive lethals, sex-chromosome loss and non-disjunction were studied following different routes of administration: adult feeding, injection and larval feeding. Our results show that, after adult injection and larval ingestion, cypermethrin induces a small but significant increase in the frequency of sex-linked recessive lethal mutations. However, no significant increases were observed in the frequency of sex chromosome loss or non-disjunction after exposure of male flies to cypermethrin at concentrations up to 20 p.p.m.

Animals↗

PubMed1997

Radioactive iodine induces clastogenic and age-dependent aneugenic effects in lymphocytes of thyroid cancer patients as revealed by interphase FISH.

After the Chernobyl nuclear accident, a dramatic 131I-related increase in the incidence of thyroid cancer has been reported in exposed children. However, little is known about the eventual genotoxic effects of 131I in exposed humans. Thyroid cancer patients are usually treated with 131I and, therefore, they provide us with an opportunity to study cytogenetic damage induced by known doses of this radionuclide. FISH techniques have been employed to study the origin of micronuclei as well as X chromosome non-disjunction and X chromosome numerical abnormalities in lymphocytes from 131I-treated women suffering from thyroid cancer. Blood was sampled before and 1 week after 131I treatment. Cells were analysed with either pancentromeric FISH to classify micronuclei or X chromosome centromere-specific FISH in mononucleated and binucleated cells to evaluate X chromosome numerical abnormalities and non-disjunction respectively. Our data indicate that 131I-induced clastogenic and age-dependent aneugenic effects in the lymphocytes of exposed patients. The X chromosome was not preferentially involved in the aneugenic effect induced by 131I. It is concluded that besides its major clastogenic effect, 131I can also induce an X chromosome-independent aneugenic activity mainly in patients with spontaneous proneness to chromosome loss.

Adolescent↗

PubMed2002

Influence of donor age on vinblastine-induced chromosome malsegregation in cultured peripheral lymphocytes.

The incidence of spontaneous aneuploidy in human somatic and germ cells is known to be positively associated with aging. However, the influence of age on the individual susceptibility to chemically induced chromosome malsegregation has not been elucidated. In this study the spindle poison vinblastine (VBL) was used as a model compound to assess the influence of donor age on chemically induced chromosome malsegregation in cultured lymphocytes. Blood cultures from 20 female donors belonging to two different age groups (10 <30 years and 10 >50 years) were treated with VBL (7.5 ng/ml) from 43 h after mitogen stimulation until harvest at 60 h, i.e. during the time interval corresponding to G2/M. In order to block cytokinesis, cytochalasin B (6 microg/ml) was added to cultures at 44 h. For each donor the incidence of micronuclei, polyploidy and malsegregation (non-disjunction and loss) of chromosomes X and 8 was determined using fluorescence in situ hybridization with chromosome-specific centromeric probes. Both background incidence of micronuclei and spontaneous chromosome X non-disjunction were significantly elevated in older donors. Individual responses to VBL treatment showed wide interindividual variability, which was not significantly associated with the age of the donor. In both age classes chromosome X was more susceptible than chromosome 8 to both spontaneous and VBL-induced malsegregation. These results indicate that donor age has a limited influence on the aneugenic effects exerted by VBL in peripheral lymphocytes in vitro. Other factors have to be considered to account for the large interindividual variation in sensitivity to VBL challenge observed in this work.

Adult↗

PubMed2002

Griseofulvin induces mitotic delay and aneuploidy in bone marrow cells of orally treated mice.

Griseofulvin (GF) is a fungicide drug well characterized for its aneugenic activity in vitro. In vivo strong evidence of aneuploidy and polyploidy induction has been obtained in germ cells, especially in oocytes. More controversial are the data on the aneugenicity of griseofulvin in somatic cells. In this paper we provide evidence that GF induces non-disjunction and cell cycle delay in bone marrow cells of orally treated mice. Adult female mice were administered olive oil suspensions of 200, 666 or 2000 mg/kg GF by gavage and killed 18 or 24 h later. To minimize animal-to-animal variation in the absorption and distribution of GF, mice were fasted from the time of GF administration to the time of killing. Two hours before treatment the animals were s.c. implanted with a bromodeoxyuridine tablet to obtain differential chromatid staining and to determine the number of divisions after GF treatment for each metaphase. Mitostatic effects of GF were assessed by the relative proportions of first, second and third generation metaphases and the average generation time (AGT) method. A statistically significant increase with respect to the control AGT value was observed after treatment with 666 and 2000 mg/kg, suggesting that GF, as already shown in meiosis, interfered with cell cycle progression. Hyperploidy was scored in second generation metaphases. Eighteen hours after treatment, the frequencies of hyperploid cells were significantly (P < 0.05) higher in all GF-treated groups than in their matched control group. The effect was not dose-dependent. No further increase in aneuploidy was observed at 24 h, suggesting that cells overcoming mitotic arrest did not have a higher rate of non-disjunction. No induction of polyploidy was demonstrated. We conclude that GF induces mitotic delay and aneuploidy in mouse bone marrow and suggest that the protocol used to formulate the gavage suspensions and the after-treatment fasting of the animals enhanced the bioavailability of GF to bone marrow cells.

Administration, Oral↗

PubMedDate not supplied

Synthesis and properties of a double translocation heterozygote involving a stable ring-of-six interchange in the German cockroach.

The synthesis and properties of a new double translocation heterozygote in B germanica, combining T (8;9) with the progressive interchange T (4;5;10), are described. Competitiveness and sterility data indicate that males are promising candidates for a "field" experiment in genetic control of a cockroach. Sterility from genetic load and embryonic trapping is complete. Disjunction properties of the parental interchanges are similar to those found in cells of the double males, but chiasma frequency of the interchanged chromosomes is increased. Evidence of a possible relationship between chiasma formation and disjunction type is discussed.

Animals↗

PubMedDate not supplied

Role of de Vries in the recovery of Mendel's work. I. Was de Vries really an independent discoverer of Mendel?

Recently, doubt has been cast on the view that de Vries developed the idea of disjunction independently of Mendel. Arguments are based on de Vries' own writings that showed the F2 data of his numerous crosses are reported as 3:1 ratios only after 1900. They also show that his theory of inheritance becomes quasi Mendelian only after 1900. The authors of this review paper cannot but agree with de Vries' critics that he did not develop his law of disjunction independently of Mendel. They also raise some questions that, hopefully, will lead to a reanalysis of de Vries' theory of inheritance in 1900.

Botany↗

PubMedDate not supplied

Spatial heterogeneity of mitochondrial DNA and allozymes among populations of white-tailed deer and mule deer.

A white-tailed deer (Odocoileus virginianus) population in northeastern Minnesota and a mule deer (O. hemionus) population in the Bridger Mountains Montana, have previously been shown to be spatially subdivided into contiguous subpopulations. We assessed the degree of genetic differentiation among subpopulations and tested the hypothesis that differentiation will be greater for mitochondrial DNA (mtDNA) than for nuclear-encoded allozymes. Differentiation of the white-tailed deer subpopulations was significant for two allozyme loci but not for mtDNA, and the overall degree of differentiation was low. Gene flow, recent founding of the subpopulations, and polygamous breeding structure may all have contributed to this pattern. Greater differentiation was evident among disjunct populations than between the contiguous subpopulations of white-tailed deer. The contiguous mule deer subpopulations were significantly differentiated for mtDNA and one allozyme locus. Differentiation was greater for mtDNA than for allozymes. These results are consistent with demographic data that indicate mule deer males disperse more than do females. Disjunct mule deer populations may be similar or dramatically different in mtDNA haplotype frequencies that do not necessarily vary with geographic distance. Current and historical gene flow and breeding structure will influence population genetic patterns.

Animals↗

PubMed1997

Tam1, a telomere-associated meiotic protein, functions in chromosome synapsis and crossover interference.

The TAM1 gene of Saccharomyces cerevisiae is expressed specifically during meiosis and encodes a protein that localizes to the ends of meiotic chromosomes. In a tam1 null mutant, there is an increase in the frequency of chromosomes that fail to recombine and an associated increase in homolog nondisjunction at meiosis I. The tam1 mutant also displays an increased frequency of precocious separation of sister chromatids and a reduced efficiency of distributive disjunction. The defect in distributive disjunction may be attributable to overloading of the distributive system by the increased number of nonrecombinant chromosomes. Recombination is not impaired in the tam1 mutant, but crossover interference is reduced substantially. In addition, chromosome synapsis is delayed in tam1 strains. The combination of a defect in synapsis and a reduction in interference is consistent with previous studies suggesting a role for the synaptonemal complex in regulating crossover distribution. tam1 is the only known yeast mutant in which the control of crossover distribution is impaired, but the frequency of crossing over is unaffected. We discuss here possibilities for how a telomere-associated protein might function in chromosome synapsis and crossover interference.

Chromosome Mapping↗

PubMed2005

Interchromosomal effect in sperm of males with translocations: report of 6 cases and review of the literature.

Somatic chromosomal abnormalities are frequently found in infertile men, particularly in those with low sperm count and/or seeking intracytoplasmic sperm injection. These abnormalities mostly consist of numerical sex chromosome abnormalities and translocations (Robertsonian or reciprocal). In this study, we searched for the occurrence of non-disjunction of chromosomes not involved in translocations during meiosis, phenomenon called interchromosomal effect (ICE) and first described by Lejeune (1965). Ejaculate samples of two patients carrying a Robertsonian translocation and four a reciprocal translocation patients and four controls (men with a 46,XY karyotype and normal sperm parameters) were studied in dual FISH 7-9, dual FISH 13-21 and triple FISH X-Y-18. A statistically significant increase of disomy X, Y and XY (P = 0.009, P = 0.004, P < 0.001) was found in the Robertsonian der(13;14)(q10;q10) carrier but not in the der(14;21)(q10;q10) carrier compared with controls. Among reciprocal translocation carriers, a significant increase of disomy 21 (P = 0.033) was observed in a sole patient with a t(9;22)(q21;q11.2). The increase of meiotic non-disjunction for chromosome 21 and sex chromosomes is a recurrent event found in other studies. According to our results and published data, the ICE on some specific chromosomes is likely in men carrier of a translocation, although it cannot be excluded that the aneuploidy is related to the oligoasthenoteratozoospermia usually present in these men. Moreover, this phenomenon showed interindividual variations which cannot be predicted. The risk of aneuploidy in sperm of males used for ICSI need to be evaluated. It could be superadded to that of meiotic segregation of the translocation to give a more precise and personalized risk assessment of aneuploidy in the offspring of those men.

Adult↗

PubMed1982

Parental origin of the extra chromosome in Down's Syndrome.

In 11 studies of patients with Down's syndrome and their parents non-disjunction was maternal in 306 cases and paternal in 77 cases. In 258 families, parental origin could not be conclusively determined. The percentage of paternal failures varied between 4.3 and 35.3% in different studies. When the type of non-disjunction was compared to the type of meiotic error, more males were born when the error was maternal (sex ratio 0.55) and more females when the error was paternal (sex ratio 0.43). An overall sex ratio of 0.52 was found. De novo translocation trisomy of type (21;21) originated paternally in one third of the cases. In (14;21) de novo translocation trisomy only one of eight cases was of paternal origin.

Adult↗

PubMed2006

Effects of Pleistocene glaciations on population structure of North American chestnut-backed chickadees.

The postglacial recolonization of northern North America was heavily influenced by the Pleistocene glaciation. In the Pacific Northwest, there are two disjunct regions of mesic temperate forest, one coastal and the other interior. The chestnut-backed chickadee is one of the species associated with this distinctive ecosystem. Using seven microsatellite markers we found evidence of population structure among nine populations of chestnut-backed chickadees. High levels of allelic variation were found in each of the populations. Northern British Columbia and central Alaska populations contained a large number of private alleles compared to other populations, including those from unglaciated regions. The disjunct population in the interior was genetically distinct from the coastal population. Genetic and historical records indicate that the interior population originated from postglacial inland dispersal. Population structuring was found within the continuous coastal population, among which the peripheral populations, specifically those on the Queen Charlotte Islands and the central Alaska mainland, were genetically distinct. The pattern of population structure among contemporary chickadee populations is consistent with a pioneer model of recolonization. The persistence of genetic structure in western North American chestnut-backed chickadees may be aided by their sedentary behaviour, linear distribution, and dependence on cedar-hemlock forests.

Alleles↗

PubMed2006

Divergence and diversity: lessons from an arctic-alpine distribution (Pardosa saltuaria group, Lycosidae).

The relationship of interpopulation genetic divergence and within-population diversity has been studied for many temperate species in Europe, but not for the cold-adapted fauna. Here we present the first European-wide phylogeographical study of an arctic-alpine distribution in invertebrates, focusing on wolf spiders of the Pardosa saltuaria group. One hundred twenty-seven (127) specimens from 14 populations were examined. Within Europe, these populations were distributed among six high mountain ranges and Scandinavia. We sequenced the whole 921 base pair mitochondrial (mt) ND1 gene. The resulting 55 unique haplotypes form three monophyletic phylogroups of deep divergence: a Pyrenean, a Balkan and a 'northern' clade. Genetic distances (3.6-4.0%) between the major clades indicate that the arctic-alpine range disjunction was initiated by vicariance events, which precede the four major Alpine glaciations. However, low divergence and incomplete lineage sorting within the 'northern clade' suggest a late Pleistocene separation of the Alpine, Scandinavian, Carpathian and Sudetian populations. Thus, we provide evidence for a multiglacial origin of arctic-alpine distributions in Europe, i.e. the current disjunction results from range fragmentation in several glacial cycles. The pattern of genetic diversity within populations seems predominantly determined by historical factors, but is modified by contemporary aspects. Overall, diversity and divergence are negatively correlated. We suggest that low diversity values might result from (i) ancient bottlenecking during warm interglacial periods, as seen in the Pyrenees and Balkans; (ii) recent bottlenecking in small modern areas, as seen in the Giant Mountains and Bohemian Forest; and (iii) dispersal bottlenecking in northern Scandinavia.

Animals↗

PubMed1984

Familial Wolf's syndrome with a hidden 4p deletion by translocation of an 8p segment. Unbalanced inheritance from a maternal translocation (4;8)(p15.3;p22). Case report, review and risk estimates.

This is the case report of a patient with Wolf's syndrome having a monosomy 4pter----p15.3 and an additional trisomy 8pter----p22, derived from a maternal balanced translocation t(4;8)(p15.3;p22) after 2:2 disjunction and adjacent-1 segregation. The patient's phenotype is presumably slightly modified by the trisomic 8p segment. Literature analyses indicate that phenotypic "hybrids" with traits of monosomy 4p and of other autosomal segment trisomies exist. The dermatoglyphics of the patient were not highly characteristic for Wolf's syndrome. Also the dermatoglyphics of the balanced translocation carriers were unspecific and did not reflect the carrier status. Pedigree analyses of 46 reported families with reciprocal translocations involving the short arm of chromosome 4 show a high risk (20.5% +/- 4.6%) for unbalanced offspring (trisomy or monosomy 4p) after 2:2 disjunction and adjacent-1 segregation, if the breakpoint in the recipient chromosome is terminal and the resulting imbalance concerns the 4p segment only. It is considerably lower (4.5% +/- 2.5%) if the breakpoint in the recipient chromosome is subterminal, as in the reported case, and the resulting imbalance concerns other chromosome segments additionally to the 4p segment. In both instances, the risk decreases with increasing segment length. The risk for unidentified abortions, stillbirths or neonatal deaths is also high in these families (about 40%). The frequency of progeny with balanced compared to progeny with normal karyotype corresponds to the expected 50% for alternate segregation.

Abnormalities, Multiple↗

PubMed1992

Consanguineous marriages among parents of Down patients.

In order to reveal if there is an effect on the genesis of meiotic- or early zygotic non-disjunctions, data related to 1598 Down syndrome patients from 1578 families studied in five different genetic centers in Turkey are reported. Parental consanguinity and the inbreeding coefficient were found to be lower among patients of 21-trisomics than in parents without Down offspring. It was concluded that available information does not support the presence of a "non-disjunction gene" in man.

Consanguinity↗

PubMed1980

Effect of maternal age on autosomal trisomies.

The effect of maternal age on the genesis of trisomy was studied by comparing data from 362 trisomic and 790 chromosomally normal spontaneous abortions. As a group the trisomies were associated with a substantial increase in maternal age but there were considerable differences in the magnitude of the effect for different trisomies. The effect of increasing maternal age was most pronounced for trisomies involving the small chromosomes, both acrocentric and non-acrocentric. However, trisomy 16 was conspicuously different from trisomies for all the other small chromosomes, both in the reduced importance of increased maternal age and in the high frequency with which it occurred. The effect of increasing maternal age on trisomies for chromosomes in groups A, B and C was less clear than that for the small chromosomes. However, the evidence suggested that trisomy for these chromosomes was associated with a moderate increase in maternal age. It was suggested that the maternal age-dependent trisomies might result from precocious disjunction of the bivalents and random segregation of the resulting univalents, a process which would affect chromosomes with the fewest number of chiasmata and which might be more prevalent if oocytes of older women. It was further suggested that true non-disjunction, that is, the failure of bivalents to separate at anaphase, might also result in the production of trisomies. This process might be independent of, or only slightly influenced by, increasing maternal age but be affected by the presence of large blocks of heterochromatin.

Abortion, Spontaneous↗

PubMed1984

Parental origin of autosomal trisomies.

Chromosome heteromorphisms of parents and their trisomic spontaneous abortions were compared in an attempt to determine the parental origin of 204 single trisomies, including cases of trisomy 3, 4, 9, 13, 14, 15, 16, 21 and 22, nine mosaic trisomies and nine double trisomies. Non-disjunction at maternal meiosis I was the most likely source of the additional chromosome for all trisomies studied, including the mosaics, and this was the case at all maternal ages. However, trisomy 21 had a significantly increased proportion of paternally derived cases by comparison with all other trisomies. Consideration of the sex ratio in cases of trisomy 21 of known parental origin suggests that there is an excess of males associated with paternal first meiotic division non-disjunction. The fact that this mechanism of origin is more prevalent in trisomy 21 may well explain why there is an excess of males associated with this abnormality but not with other autosomal trisomies.

Abortion, Spontaneous↗

PubMed1988

Origin of sex chromosome aneuploidy.

Probabilities applicable to RFLPs are derived for the genotypes of XXY, XXX, and XO children, conditional on their mode of origin and the parental mating type, and the theory is applied to family data on the XG locus. The proportion of XXY males arising in spermatogenesis is shown to be 0.41 +/- 0.09. The large distance of XG from the centromere makes distinction between maternal meiosis I and II unreliable, but if man is like Drosophila, most of the maternal non-disjunctions arise in meiosis I, among tetrads that have undergone one or more exchanges. Data from XG show that 0.78 +/- 0.05 of XO females arise from an error involving the paternal sex chromosomes. The XG locus is virtually uninformative about the origin of XXX. Application of the theory to selected RFLPs will be much more incisive because of their large number, lack of dominance, greater heterozygosity, and distribution along the chromosome. Study of RFLPs will facilitate diagnosis of the parental origin of sex chromosome abnormalities and the comparison of recombination rates in regular and trisomic progeny of maternal mei I and mei II origin. A pseudocentromeric model that estimates map distances from exceptional progeny is applied to non-disjunction of the X chromosomes in D. melanogaster, giving good recovery of the expected map and thereby validating this approach for RFLPs in man.

Aneuploidy↗

PubMed1988

Klinefelter's syndrome: an analysis of the origin of the additional sex chromosome using molecular probes.

The results of our study of the origin of the additional X chromosome in 39 males with a 47,XXY chromosome constitution are reported. We used a total of 20 X-linked RFLPs and successfully determined the origin of all 32 patients in whom DNA from both parents was available, and a further 3 in whom DNA was available from the patient and mother only. Males whose additional X chromosome was maternal in origin were further investigated using an X-linked centromere specific probe to determine the cell division at which the error occurred. Our results showed 53% of the non-disjunction to be attributable to pat mei I errors, 34% to mat mei I errors, 9% to mat mei II errors and 3% to a post-zygotic mitotic error. In the great majority of patients resulting from an error of maternal meiosis there was clear evidence of recombination involving the non-disjoined chromosomes, suggesting that absence of recombination is not an important aetiological factor in non-disjunction of the X chromosome in female meiosis. There was no alteration of parental age associated with the paternally derived 47,XXY males but a marked increase in maternal age among the maternally derived 47,XXY males, the increase being associated with mat mei I but not mat mei II errors. The proportion of paternally and maternally derived cases was similar among different ascertainment classes, suggesting that there is no dramatic effect of parental origin of the additional X chromosome on the phenotype of 47,XXY males.

Age Factors↗