No induction of interchromosomal effect in male meiosis of Chinese hamsters with reciprocal translocations

Chinese hamsters from five strains with reciprocal translocations, T(1;3)7Idr, T(1;3)8Idr, T(1;2)9Idr, T(7;9)16Idr, and T(1;5)17Idr, and a karyotypically normal strain, CHS/Idr, were used to look for an interchromosomal effect by chromosomal analysis of meiotic cells and one-cell embryos. The frequencies of nondisjunction at first meiosis in five normal (+/+) males, calculated by doubling the number of hyperhaploid cells, ranged from 0.43% to 1.33%, and there was no significant difference in frequency among individuals. On the other hand, the frequency of hyperhaploid cells in males heterozygous for each translocation ranged from 3.0% to 11.8%, and the frequency of hyperhaploid cells with an extra translocation-unrelated chromosome ranged from 0.2% to 0.4%, which is no different from that estimated from scoring of +/+ males at the second meiotic metaphase. In one-cell embryos from crosses between karyotypically normal females and male heterozygotes for T(1;2)9Idr and T(7;9)16Idr, 1.1% and 0.5% of embryos had an extra translocation-unrelated chromosome. Compared with the control, the frequency of meiotic nondisjunction showed no increase in male heterozygotes for the reciprocal translocations. Therefore, the results suggest that multivalents and rearranged chromosomes existing at first and second meiosis in male Chinese hamsters exert no influence on segregation of normal bivalents and chromosomes unrelated to the rearrangements.     

Failure of chromosomally abnormal sperm to participate in fertilization in the Chinese hamster.

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.     

Transmission of chromosomal abnormalities: participation of chromosomally unbalanced gametes in fertilization and early development of unbalanced embryos in the Chinese hamster

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.     

Meiotic mutations from natural populations ofDrosophila melanogaster

Two meiotic genes from natural populations are described. A female meiotic mutation,mei(1)g13, mapped to 17.4 on the X chromosome, causes nondisjunction of all homologs except for the fourth chromosomes. In addition, it reduces recombination by 10% in the homozygotes and causes 18% increased recombination in the heterozygotes. A male meiotic mutation,mei-1223 ^m144 , is located on the third chromosome. Although this mutation causes nondisjunction of all chromosomes, each chromosome pair exhibits a different nondisjunction frequency. Large variations in the sizes of the premature sperm heads observed in the homozygotes may reflect irregular meiotic pairing and the subsequent abnormal segregation, resulting in aneuploid chromosome complements.     

Une triple translocation chez le Triton Pleurodeles waltlii

A cytogenetic study has lead us to a stock of fertile heterozygotes for a triple translocation. The chromosomal rearrangement has first been detected in a female resulting from a cross between a normal female and a male submitted to X ray-irradiation. The aberration consists of rearrangements between a chromosome 3, a chromosome 6 and a chromosome 7. Abnormal chromosomes have the following constitution: 7q?: the terminal portion of the long arm is lost and replaced by the end of the short arm of the chromosome 3. 6 q+: the terminal portion of the long arm is lost and replaced by the end of the long arm of the chromosome 7. 3p+: the terminal portion of the short arm is lost and replaced by the end of the long arm of the chromosome 6. On the analogy of the human chromosome standardization, the formula of heterozygotes is 24, t (3p+, 6q+, 7q?). The first meiotic division shows both in the female and in the male 9 bivalents and one hexavalent. The formulae of the gametes are the same in both sexes. When a heterozygote is bred with a normal individual the offspring is composed of phenotypically normal or abnormal animals, depending on their karyotypes. The unbalanced karyotypes are lethal or semilethal. The importance of the malformations depends on the temperature of the water where the animals grow. The study of the meiotic slides brings a cytological confirmation of the results obtained from the study of the phenotypes and karyotypes which appear in the offspring.     

Meiotic nondisjunction and translocation segregation in dwarf (dw/dw) and control T(1;13)70H heterozygous mice

The meiotic behavior of translocation heterozygous T70 (1;13)H/+ male mice with a Snell dwarf (dw/dw) genotype was compared with that of nondwarf T70H/+ controls. A four-fold increase in the nondisjunction frequency of the normal bivalents occurred as a consequence of the dwarf genotype. This increase is identical to that seen in karyologically normal dwarf males. No effect of the dwarf condition on the segregation of the translocation multivalent could be noted. Thus, translocation heterozygosity does not enhance the meiotic instability caused by the hypopituitary dwarf condition. From a small sample of oocytes from T70H/+ and chromosomally normal dwarf females it is concluded that nondisjunction in females is not increased by the dwarf condition. In general we conclude that animals with higher spontaneous nondisjunction levels are not necessarily more sensitive to factors increasing nondisjunction.     

Contribution of chromosomal imbalance to sperm selection and pre-implantation loss in translocation-heterozygous Chinese hamsters

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.     

Meiotic exchange and segregation in female mice heterozygous for paracentric inversions

Inversion heterozygosity has long been noted for its ability to suppress the transmission of recombinant chromosomes, as well as for altering the frequency and location of recombination events. In our search for meiotic situations with enrichment for nonexchange and/or single distal-exchange chromosome pairs, exchange configurations that are at higher risk for nondisjunction in humans and other organisms, we examined both exchange and segregation patterns in 2728 oocytes from mice heterozygous for paracentric inversions, as well as controls. We found dramatic alterations in exchange position in the heterozygotes, including an increased frequency of distal exchanges for two of the inversions studied. However, nondisjunction was not significantly increased in oocytes heterozygous for any inversion. When data from all inversion heterozygotes were pooled, meiotic nondisjunction was slightly but significantly higher in inversion heterozygotes (1.2%) than in controls (0%), although the frequency was still too low to justify the use of inversion heterozygotes as a model of human nondisjunction.     

Meiotic segregation of human sperm chromosomes in translocation heterozygotes: report of a t(9;10)(q34;q11) and a review of the literature

Meiotic segregation products were studied in sperm from a man who was heterozygous for a reciprocal translocation, t(9;10)(q34;q11). A total of 171 sperm chromosome complements were studied by in vitro fertilization of hamster eggs. All possible 2:2 and 3:1 meiotic segregations were observed with the following frequencies: alternate, 41%; adjacent-1, 48%; adjacent-2, 5%; 3:1, 6%. Within alternate segregations, the number of normal sperm (35) was not significantly different from the number of sperm carrying a balanced form of the translocation (33), as expected. The proportion of sperm with an unbalanced form of the translocation was 60%. There was no evidence for an interchromosomal effect, since the frequencies of numerical (8%) and structural (15%) chromosomal abnormalities (both unrelated to the translocation) were within the normal range of control donors. The literature on a total of 10 translocation heterozygotes studied by sperm chromosome analysis was reviewed.     

Aneuploidy in the embryonic progeny of females heterozygous for the Robertsonian chromosome (9.12) in genetically wild Peru-Coppock mice (Mus musculus)

The spontaneous appearance of a Robertsonian translocation in a laboratory colony of genetically wild Peru-Coppock mice gave the opportunity to study potential meiotic nondisjunction soon after the formation of the new chromosome and also in a hitherto untested combination of genotype and environment Metaphase II scores from the progenitor male had indicated a nondisjunction rate of approximately 10%, a figure that was confirmed by the finding of an estimated 12-16% total trisomic and probable monosomic zygotes in chromosomal studies of Day 9 embryos from heterozygous females. The chromosome studies also showed the presence of a significant excess of normal embryos that were heterozygous for the Robertsonian chromosome.     

Pachytene analysis in males heterozygous for a familial translocation (9;12;13) (q22; q22; q32) ascertained through a child with partial trisomy 9

A family with four male and three female heterozygotes for a three-way translocation (9;12;13) (q22; q22; q32) in three generations was ascertained through a chromosomally imbalanced newborn with an additional derivative chromosome 9 resulting from nondisjunction. Three heterozygous males from two generations with apparent differences in their fertility status were investigated using pachytene spreads and testicular histology. Pachytene analysis in all three individuals, the fertile (II-2) as well as the subfertile (III-7) and infertile (III-9), showed a hexavalent with central nonpairing around the translocation breakpoints in nearly all spermatocytes. Thus, the observed hexavalent configurations in pachytene do not seem to have caused impaired fertility. This rather may have been the result of sperm carrying unbalanced chromosome sets. However, the observed difference in fertility between the heterozygous fertile male in generation II and his two heterozygous sons remains unexplained.     

Analysis of meiotic segregation in a man heterozygous for a 13;15 Robertsonian translocation and a review of the literature

Summary Meiotic segregation was studied in a male heterozygous for a 13;15 Robertsonian translocation using in vitro sperm penetration of hamster eggs. Sixty-seven sperm chromosome complements were obtained and R-banded. Alternate segregation produced equal numbers of normal (31) and balanced (29) gametes, as was theoretically expected. Incidence of unbalanced complements was 10.4%, and the frequency of abnormalities unrelated to the translocation was 7.4%. This study confirms the predominance of alternate meiotic segregation in Robertsonian translocation carriers. Four sperm studies of Robertsonian translocation have been previously reported. A review of the combined results points out the low incidence of imbalance in the sperm of Robertsonian translocation carrier and the lack of evidence for an interchromosomal effect.     

Molecular analysis of nondisjunction in mice heterozygous for a Robertsonian translocation

A Robertsonian translocation results in a metacentric chromosome produced by the fusion of two acrocentric chromosomes. Rb heterozygous mice frequently generate aneuploid gametes and embryos, providing a good model for studying meiotic nondisjunction. We intercrossed mice heterozygous for a (7.18) Robertsonian translocation and performed molecular genotyping of 1812 embryos from 364 litters with known parental origin, strain, and age. Nondisjunction events were scored and factors influencing the frequency of nondisjunction involving chromosomes 7 and 18 were examined. We concluded the following: 1. The frequency of nondisjunction among 1784 embryos (3568 meioses) was 15.9%. 2. Nondisjunction events were distributed nonrandomly among progeny. This was inferred from the distribution of the frequency of trisomics and uniparental disomics (UPDs) among all litters. 3. There was no evidence to show an effect of maternal or paternal age on the frequency of nondisjunction. 4. Strain background did not play an appreciable role in nondisjunction frequency. 5. The frequency of nondisjunction for chromosome 18 was significantly higher than that for chromosome 7 in males. 6. The frequency of nondisjunction for chromosome 7 was significantly higher in females than in males. These results show that molecular genotyping provides a valuable tool for understanding factors influencing meiotic nondisjunction in mammals.     

Influence of ethanol on chromosome segregation during the first and second meiotic divisions in the mouse egg

This study was carried out to investigate the influence of ethanol on chromosome segregation during the first and second meiotic divisions. Female mice were given a single intragastric injection of a dilute solution of ethanol either just before or at various times after the HCG injection for inducing superovulation. The mice were mated, and the chromosome constitution of fertilized eggs was determined at the first cleavage mitosis. The technique employed allowed the male- and female-derived pronuclear sets to remain as two discrete groups. Exposure from 1.5 h before to 17 h after the HCG injection induced a high incidence of aneuploidy (15-25%) involving in over 90% of cases only one chromosome, so that either 19 or 21 instead of the normal complement of 20 chromosomes were present in one of the two sets (a previous study using a "marker" chromosome has demonstrated that the nondisjunction induced here invariably involves the female set). We suggest these findings draw attention to the susceptibility of chromosome segregation in female germ cells to interference by ethanol and that the mode of action is likely to be via interference with the normal functioning of the spindle apparatus. It is possible that interference with meiotic chromosome segregation by spindle-acting agents such as ethanol might account for a proportion of human spontaneous abortions with similar chromosomal defects where no other obvious cause is apparent.     

Selective elimination of chromosomally unbalanced zygotes at the two-cell stage in the Chinese hamster

The gametic and zygotic selection of genome imbalance was investigated in the Chinese hamster by direct chromosome analyses of spermatocytes and preimplantation embryos from crosses between chromosomally normal females and males heterozygous for a reciprocal translocation, T(2;10)3Idr, abbreviated here as T3. The karyotypes and the frequencies of embryos observed at the first cleavage in the cross +/+female X T3/+male were consistent with those expected from MII scoring in male T3 heterozygotes. Therefore, it was concluded that there was neither gametic selection against genome imbalance nor zygotic selection from fertilization until the first cleavage metaphase. However, 9.1-10.8% of embryos were arrested at the two-cell stage, and karyotypes of these embryos were confirmed as 22(2,10,10,10(2)), 21(2,10,10), and 21(2,10,10(2)). The common abnormality of these embryos was partial monosomy of chromosome 2. Among day 4 embryos, some chromosomally unbalanced embryos, mainly with a deficiency of other segments of chromosomes 2 and 10, had fewer blastomeres than chromosomally balanced embryos. This finding suggests that cleavage of these embryos had been retarded by day 4 of gestation.     

Isolation of telotertiary compensating trisomics from telocentric translocation trisomics and telo-substituted translocation heterozygotes of rye (Secale cereale L.)

Telotertiary compensating trisomics (CTs) of rye (Secale cereale L.), in which the absence of one normal chromosome is compensated by the presence of a telocentric and a translocation chromosome, were isolated in progenies of telocentric translocation trisomics, and telo-substituted translocation heterozygotes, respectively. These two sources were obtained from crosses between five interchanges of the Wageningen translocation tester set, and telocentric normal trisomics (for IRS, IRL and 5RS), or telocentric substitutions (for IR and 3R), respectively. In test crosses with normal male plants, CTs were identified using either critical meiotic configurations, the segregation of karyotypes in selfed trisomic progenies, or the segregation of a marker located on the compensated chromosome. CT yields ranged from 0.0–6.3%. These frequencies were concluded to be determined mainly by the frequency of the exchanged segment of the translocation chromosome involved in the CT complex being associated at first meiotic metaphase (MI) in the source plants. The lower association frequencies result in the higher CT yields. The correlation between high association frequency of this segment and low CT yield suggests that infrequent adjacent orientation of one critical segment is also responsible for the origin of CTs. This agrees with cytogenetic theory.     

Nondisjunction and chromosome breakage in mouse oocytes after various X-ray doses

Summary The effect of varying X-ray doses (0.05–0.80 Gy) on preovulatory mouse oocytes was studied by measuring nondisjunction during the first meiotic division, as well as structural chromosome anomalies in ovulated oocytes at metaphase stage II. The incidence of nondisjunction (0.1% hyperploid oocytes) found in oocytes from nonirradiated NMRI-Han female mice was in accordance with the results previously obtained with the same strain. Significantly (P<0.05) more hyperploid oocytes (0.9%) were ovulated following irradiation with 0.8 Gy. There was no statistically significant increase of nondisjunction after low doses. Structural chromosome anomalies occurred, however, even after an irradiation dose as low as 0.05 Gy. The dose response for structural chromosome anomalies is altogether different from that of radiation-induced hyperpoidy. We consider that irradiation of mature oocytes might well be less hazardous with regard to its potency for increasing nondisjunction during the first meiotic division when compared with the effect of chemical mutagens.     

Genetic Analysis of Sex Chromosomal Meiotic Mutants in DROSOPHILA MELANOGASTER

A total of 209 ethyl methanesulfonate-treated X chromosomes were screened for meiotic mutants that either (1) increased sex or fourth chromosome nondisjunction at either meiotic division in males; (2) allowed recombination in such males; (3) increased nondisjunction of the X chromosome at either meiotic division in females; or (4) caused such females, when mated to males heterozygous for Segregation-Distorter (SD) and a sensitive homolog to alter the strength of meiotic drive in males.-Twenty male-specific meiotic mutants were found. Though the rates of nondisjunction differed, all twenty mutants were qualitatively similar in that (1) they alter the disjunction of the X chromosome from the Y chromosome; (2) among the recovered sex-chromosome exceptional progeny, there is a large excess of those derived from nullo-XY as compared to XY gametes; (3) there is a negative correlation between the frequency of sex-chromosome exceptional progeny and the frequency of males among the regular progeny. In their effects on meiosis these mutants are similar to In(1)sc(4L)sc(8R), which is deleted for the basal heterochromatin. These mutants, however, have normal phenotypes and viabilities when examined as X/0 males, and furthermore, a mapping of two of the mutants places them in the euchromatin of the X chromosome. It is suggested that these mutants are in genes whose products are involved in insuring the proper functioning of the basal pairing sites which are deleted in In(1)sc(4L)sc(8R), and in addition that there is a close connection, perhaps causal, between the disruption of normal X-Y pairing (and, therefore, disjunction) and the occurrence of meiotic drive in the male.-Eleven mutants were found which increased nondisjunction in females. These mutants were characterized as to (1) the division at which they acted; (2) their effect on recombination; (3) their dominance; (4) their effects on disjunction of all four chromosome pairs. Five female mutants caused a nonuniform decrease in recombination, being most pronounced in distal regions, and an increase in first division nondisjunction of all chromosome pairs. Their behavior is consistent with the hypothesis that these mutants are defective in a process which is a precondition for exchange. Two female mutants were allelic and caused a uniform reduction in recombination for all intervals (though to different extents for the two alleles) and an increase in first-division nondisjunction of all chromosomes. Limited recombination data suggest that these mutants do not alter coincidence, and thus, following the arguments of Sandler et al. (1968), are defective in exchange rather than a precondiiton for exchange. A single female mutant behaves in a manner that is consistent with it being a defect in a gene whose functioning is essential for distributive pairing. Three of the female meiotic mutants cause abnormal chromosome behavior at a number of times in meiosis. Thus, nondisjunction at both meiotic divisions is increased, recombinant chromosomes nondisjoin, and there is a polarized alteration in recombination.-The striking differences between the types of control of meiosis in the two sexes is discussed and attention is drawn to the possible similarities between (1) the disjunction functions of exchange and the process specified by the chromosome-specific male mutants; and (2) the prevention of functional aneuploid gamete formation by distributive disjunction and meiotic drive.     

Male pachytene pairing in single and double translocation heterozygotes and spermatogenic impairment in the mouse

In order to clarify the relationship between meiotic pairing and progress of spermatogenesis, an analysis of male meiotic pairing was carried out in four reciprocal translocation heterozygotes and two double heterozygotes for two semi-identical reciprocal translocations. The reciprocal translocations were chosen to range from fertility (T70H/+) through almost complete sterility (T31H/+) to complete sterility (T32H/+, T42/H+). If meiotic pairing in the translocation multivalent was incomplete, it concerned terminal or probably more often proximal chromosome segments (Chain IV). If both segments failed to pair the multivalent symbol is Chain III+I. Complete pairing is symbolized by Ring IV. To contrast and complement observations of this type, the double heterozygotes were introduced. Males of this type in theory possess two heteromorphic bivalents with a central area of incomplete meiotic pairing (loop formation). Of the T70H/T1Wa double heterozygotes, 36% of the males are capable of inducing at least one decidual reaction in two females whereas for T26H/T2Wa, 79% of the males can do so. For the reciprocal translocations, it was found that proximity of the multivalent to the sex bivalent during pachytene increased in the order Ring IV, Chain IV, Chain III+I. The degree of spermatogenic impairment as measured from cell counts in histological sections and tubular whole mounts, is positively related to the frequency of proximity between the sex chromosomes and the translocation multivalent and thus to lack of meiotic pairing within the multivalent. The meiotic pairing analysis of the double heterozygotes yielded the following findings. For the long heteromorphic bivalents a true loop was never seen in T70H/T1Wa and only rarely observed in T26H/T2Wa. Small marker bivalents of both types were usually recognizable by the following criteria: (i) pairing confined to distal or proximal segments, (ii) both distal and proximal segments pairing and loop formation and (iii) pairing covering the entire length of both homologues but the longer one often with a thickened lateral element. The same positive correlation between the absence of pairing (proximal, distal or central) and the proximity of the small marker bivalent synaptonemal complex to the sex bivalent has been found as for unpaired segments within reciprocal translocation multivalents. One unexpected finding was the occurrence of diploid spermatids and spermatozoa especially in T32H/+ males (70–91%) but also in T31H/+ (3–39%).     

Ethanol-induced aneuploidy in male germ cells of the mouse

The administration of alcohol to male mice 2-6 h before the preparation of second meiotic metaphases from testes resulted in an approximately six-fold increase in aneuploidy. The timing employed indicates that the observed chromosome abnormalities were a result of nondisjunction and/or anaphase lagging at the first meiotic division. A similar effect has been described in the female mouse; however, the present results suggest that the aneuploidy-inducing effect of ethanol may be substantially greater in the female than in the male.