Meiotic Abnormalities Research Articles

Revisiting Meiosis in Sugarcane: Chromosomal Irregularities and the Prevalence of Bivalent Configurations.

Traditional sugarcane cultivars (Saccharum officinarum) proved highly susceptible to diseases, and this led breeders to progress to interspecific crosses resulting in disease resistance. A backcrossing program to S. officinarum was then required to boost sucrose content. Clonal selection across generations and incorporation of other germplasm into cultivated backgrounds established the (narrow) genetic base of modern cultivars (Saccharum spp.), which have a man-made genome. The genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture, and cytogenetics. However, there is a critical shortage of information on chromosome behavior throughout meiosis in modern cultivars. In this study, we examined the microsporogenesis of a contemporary variety, providing a detailed analysis of the meiotic process and chromosome association at diakinesis, using FISH with centromeric probes. Chromosomal abnormalities were documented by examining high quality preparations of pollen mother cells (700 in total). Approximately 70% of the cells showed abnormalities, such as metaphase chromosomes not lined up at the plate, lagging chromosomes and chromosomal bridges, and tetrad cells with micronuclei. Some dyads with asynchronous behavior were also observed. Due to the hybrid composition of the sugarcane genome, we suggest that bivalent incomplete pairing may occur in the first prophase leading to univalency. The presence of rod bivalents showing the lagging tendency is consistent with a reduction in chiasma frequency. Finally, the presence of chromatin bridges indicates the indirect occurrence of chromosomal inversions, although chromosome fragments were not clearly recognized. Possible reasons for such meiotic abnormalities and the large prevalence of bivalent formation are discussed.

Molecular cytogenetic characterization, leaf anatomy and ultrastructure of the medicinal plant Potentilla alba L.

Potentilla alba L. is a valuable medicinal plant widely used in folk and traditional medicine and particularly promising in complex treatment of thyroid pathology. Natural resources of this species are insufficient due to ever-growing use in contemporary medicine. Comprehensive investigations of different P. alba populations are essential for the successful extension of P. alba plantings. Aiming for a better understanding of karyotype structure, chromosome behaviour in meiosis and developing new diagnostic characters, we performed molecular cytogenetic characterization and leaf structure and ultrastructure analyses of two introduced P. alba samples originating from different habitats. Based on chromosome morphology, distribution of 45S/5S rDNA and DAPI-banding patterns, all chromosomes in the karyotypes were identified and the P. alba chromosomal idiogram was constructed. Our findings confirmed P. alba karyotype stability and also revealed several diagnostic characters of this species: the features of cells of upper and lower leaf epidermis, the presence of calcium oxalate druses and three types of leaf indumentum, essential for evaluation of genetic diversity in different populations, validation of raw materials and further selection progress. The meiotic abnormalities were detected probably related to low pollen activity and indicated the advantages of vegetative propagation in the development of a P. alba plantation system.

Male meiosis in 18 species of 07 genera of the tribe Astereae (Asteraceae) from Western Himalaya

Meiotic studies in 18 species belonging to 7 genera of the tribe Astereae from various localities of Western Himalaya have been analyzed. The chromosome number has been reported for the first time in Aster albescens (n = 9) and A. indamellus (n = 9). Further, intraspecific variability has been reported for the first time in A. thomsonii (n = 27), Bellis perennis (n = 5) and Myriactis nepalensis (n = 18). In India, the chromosome numbers are reported for first time in Aster himalaicus (n = 9), Brachyactis roylei (n = 9), Erigeron bellidioides (n = 9) and E. borealis (n = 9). B-chromosomes have been reported for the first time in Erigeron acer (n = 9 + 1 − 2B). Besides, most of the populations show laggards, chromosome stickiness and cytomixis from early prophase to telophase-II, leading to the formation of aneuploid cells or meiocytes with doubled chromosome number. Such meiotic abnormalities produce unreduced pollen grains and adversely affect pollen viability.

Study of the Cytogenetical Effects on Meiotic Chromosomal Abnormalities Induced by Mutagens in Soybean

Study of the Cytogenetical Effects on Meiotic Chromosomal Abnormalities Induced by Mutagens in Soybean

Cytogenetic evaluation of chili (Capsicum spp., Solanaceae) genotypes cultivated in Valle del Cauca, Colombia

The genus Capsicum comprises a large group of hot and sweet peppers, with different morphological varieties and degree of fruits pungency. Due to its active principles is widely used in cooking and in traditional medicine, being sold in large worldwide. In order to provide cytogenetic information which supporting plant breeding programs, this study aimed to analyze the meiotic behavior, chromosome number and pollen viability of the three species of greater economic importance of Capsicum (C. annuum, C. frutescens and C. chinense). Therefore, fruits and flower buds were collected from the Experimental Center of the Universidad Nacional de Colombia, campus Palmira- CEUNP to the corresponding mitotic, meiosis and pollen viability analysis. Plants presented different meiotic abnormalities, where all can disrupt the process of meiosis cell division, creating unbalanced chromosome numbers and varied pollen fertility. Chromosome number variation, checking 2n=2x=24, 2n=2x=26, 2n=4x=48 to 2n=6x=72 chromosomes also occurred. A low degree of non-viable pollen grains was observed for C. frutescens, so these accession should not considered as a parental for plant breeding programs.

Peritoneal Fluid From Infertile Women With Minimal/Mild Endometriosis Compromises the Meiotic Spindle of Metaphase II Bovine Oocytes: A Pilot Study

Some studies have demonstrated alterations in the composition of peritoneal fluid (PF) from women with endometriosis. Controversial studies have suggested that impaired oocyte quality may be involved in the pathogenesis of endometriosis-related infertility. The aim of this study was to evaluate the spindle and chromosome distribution of in vitro-matured oocytes in the presence of 2 concentrations of PF from infertile women with minimal/mild endometriosis (EI/II) compared to fertile controls. We performed an experimental study using a bovine model. Samples of PF were obtained from 12 women who underwent videolaparoscopy-6 infertile women with EI/II and 6 fertile women without endometriosis (control group). Immature bovine oocytes underwent in vitro maturation (IVM) in the absence of PF and in the presence of 2 concentrations (1% and 10%) of PF from fertile women and from infertile women with EI/II. After 22 to 24 hours of IVM, oocytes were fixed for subsequent immunofluorescence staining for the visualization of microtubules and chromosomes by confocal microscopy. The percentage of meiotically normal oocytes was significantly lower for oocytes that underwent IVM in the presence of 1% (62.50%) and 10% (56.25%) of PF from infertile women with EI/II than in the absence of PF (88.46%) and in the presence of 1% (78.57%) and 10% (84.61%) of PF from fertile women ( P < .01). We demonstrated that PF from infertile women with EI/II promotes meiotic abnormalities in in vitro-matured bovine oocytes. Therefore, our results contribute to the understanding of the etiopathogenic mechanisms of infertility related to EI/II.

Meiotic chromosome behavior of the male-fertile allotriploid lily cultivar 'Cocossa'.

Cytological observations of microsporogenesis in the allotriploid lily cultivar 'Cocossa' showed that viable pollen production could be attributed mainly to disoriented spindles, abnormal cytokinesis, and cytomixis during male meiosis. To identify the reasons why the allotriploid lily cultivar 'Cocossa' can produce aneuploid and euploid functional male gametes and can be used as the paternal parent in lily introgression breeding, we performed a detailed investigation of microsporogenesis using the conventional cytological methods. The allotriploid not only produced single pollen grains with variable sizes but also produced adherent pollen grains. Pollen viability was estimated at 50.1% based on staining and 30.8% based on germination. Based on the chromosomal analysis of BC2 plants derived from Oriental cultivars (♀) crossed with the OOT cultivar 'Cocossa' (♂), it was concluded that the objective allotriploid contributed haploid (x), diploid (2x), and aneuploid chromosome complements. Common meiotic abnormalities were observed, indicating the high genetic imbalance of this allotriploid. In addition to normally oriented metaphase II spindles (linear and perpendicular), abnormal spindles, such as parallel, tripolar, fused, and multiple spindles, accounted for 6.21, 6.41, 14.27, and 1.17%, respectively. Tripolar and fused spindles resulted in the production of triads and dyads, which contributed to unreduced pollen production. Some microsporocytes exhibited complete or partial absence of cytokinesis, which led to relatively high frequencies of monads, dyads, and triads. Furthermore, the phenomenon of cytomixis during microsporogenesis occurred mainly in the first meiotic prophase and early development of pollen grains, which we assume is a possible cause of unreduced gamete generation. Our study offers a new resource for lily introgression breeding.

Abnormal meiosis in an intersectional allotriploid of Populus L. and segregation of ploidy levels in 2x × 3x progeny.

Triploid plants are usually highly aborted owing to unbalanced meiotic chromosome segregation, but limited viable gametes can participate in the transition to different ploidy levels. In this study, numerous meiotic abnormalities were found with high frequency in an intersectional allotriploid poplar (Populus alba × P. berolinensis ‘Yinzhong’), including univalents, precocious chromosome migration, lagging chromosomes, chromosome bridges, micronuclei, and precocious cytokinesis, indicating high genetic imbalance in this allotriploid. Some micronuclei trigger mini-spindle formation in metaphase II and participate in cytokinesis to form polyads with microcytes. Unbalanced chromosome segregation and chromosome elimination resulted in the formation of microspores with aneuploid chromosome sets. Fusion of sister nuclei occurs in microsporocytes with precocious cytokinesis, which could form second meiotic division restitution (SDR)-type gametes. However, SDR-type gametes likely contain incomplete chromosome sets due to unbalanced segregation of homologous chromosomes during the first meiotic division in triploids. Misorientation of spindles during the second meiotic division, such as fused and tripolar spindles with low frequency, could result in the formation of first meiotic division restitution (FDR)-type unreduced gametes, which most likely contain three complete chromosome sets. Although ‘Yinzhong’ yields 88.7% stainable pollen grains with wide diameter variation from 23.9 to 61.3 μm, the pollen viability is poor (2.78% ± 0.38). A cross of ‘Yinzhong’ pollen with a diploid female clone produced progeny with extensive segregation of ploidy levels, including 29 diploids, 18 triploids, 4 tetraploids, and 48 aneuploids, suggesting the formation of viable aneuploidy and unreduced pollen in ‘Yinzhong’. Individuals with different chromosome compositions are potential to analyze chromosomal function and to integrate the chromosomal dosage variation into breeding programs of Populus.

High temperature-induced production of unreduced pollen and its cytological effects in Populus

Temperature change is of potential to trigger the formation of unreduced gametes. In this study, we showed that short periods of high temperature treatment can induce the production of 2n pollen in Populus pseudo-simonii Kitag. The meiotic stage, duration of treatment, and temperature have significant effects on the induction of 2n pollen. Heat stress resulted in meiotic abnormalities, including failure of chromosome separation, chromosome stickiness, laggards and micronuclei. Spindle disorientations in the second meiotic division, such as parallel, fused, and tripolar spindles, either increased in frequency or were induced de novo by high temperature treatment. We found that the high temperature treatment induced depolymerisation of meiotic microtubular cytoskeleton, resulting in the failure of chromosome segregation. New microtubular cytoskeletons were able to repolymerise in some heat-treated cells after transferring them to normal conditions. However, aberrant cytokinesis occurred owing to defects of new radial microtubule systems, leading to production of monads, dyads, triads, and polyads. This suggested that depolymerisation and incomplete restoration of microtubules may be important for high temperature-induction of unreduced gametes. These findings might help us understand how polyploidisation is induced by temperature-related stress and support the potential effects of global climate change on reproductive development of plants.

Meiotic behaviour and morpho-phenological variation in cut stock (Matthiola incanaL.) flower

AbstractMorpho-phenological and meiotic studies were performed in twelve cultivars of Matthiola incana. All of the cultivars were diploid (2n = 2x = 14) with basic chromosome number x = 7. A number of aneuploid PMCs (n + 1) were observed in plants of two cultivars, named ‘Nobel’ (NB) and ‘Goddess’ (GD), at the diakinesis stage. Trisomic individuals with the frequency of 20% and 5% and (2n + 1 = 15) somatic chromosomes were observed in seeds obtained from single-flowered plants of the cultivars NB and GD, respectively. An additional chromosome was mostly observed in the form of a chain trivalent or a rod univalent. Various meiotic abnormalities were found in all the cultivars to different degrees. In these cultivars, the percentage of cells with meiotic abnormalities was higher in anaphase I. Cytomixis was observed for the first time in Matthiola incana. ANOVA tests revealed significant differences in morpho-phenological characteristics. ‘Nobel’ differs from the others in all of the vegetative features investigated in this study. All the cultivars studied except ‘Nobel’ and ‘Pacific Crimson’ possessed high pollen fertility (&gt; 90%). Five groups of the cultivars based on morpho-phenological features disagree with the clustering of cultivars based on meiotic traits. It is thought that the various morpho-phenological features observed among the cultivars could be due to their different genetic background and not only to meiotic anomalies.

Mitotic and meiotic studies on two species of Ocimum (Lamiaceae) and their F1hybrids

AbstractOcimum L. species are important aromatic and medicinal plants. Many researchers have observed complexity in their chromosome numbers and ploidy levels. We studied the somatic and germline chromosomal features and behaviour of Ocimum basilicum L., two variants of O. canum Sims (‘c1’ and ‘c2’) and their F1hybrids. Chromosomes from root tips and flower buds were investigated using standard techniques; karyograms were formed and analysed. A chromosome number of 2n = 4x = 52 was observed in O. basilicum and O. canum ‘c1’ and their F1hybrid. One of the variants, O. canum ‘c2’ had a chromosome number of 2n = 2x = 24 and its intraspecific hybrid O. canum ‘c2’ × O. canum ‘c1’ had a chromosome number of 2n = 38. These Ocimum species and their F1hybrids showed different karyotype formula, but their chromosomes were mostly metacentric (174) and submetacentric (36) with few subtelocentric (8). Based on pairing configuration, O. basilicum is an allotetraploid plant, O. canum ‘c1’ is an autotetraploid plant and the O. canum ‘c1’ is a diploid. The F1 hybrids showed higher frequency of meiotic abnormalities than the parents. The study showed intraspecific and interspecific variation in chromosome numbers and pairing patterns, but the chromosomes of the Ocimum species were similar in their centromeric positions.

Morphological studies and meiotic chromosome analysis of Epimedium elatum (Morr &amp; Decne) - Rare endemic medicinal plant of Northwestern Himalayas in India.

&lt;p&gt;&lt;em&gt;Epimedium elatum&lt;/em&gt; (Berberidaceace) is a rare endemic medicinal herb of Northwestern Himalayas in India. Recent ethnopharmacological reports have demonstrated its traditional medicinal use against various bone related diseases in the Kashmir Himalayas. It owes its pharmaceutical importance due to high concentration of flavonoid glycosides like Epimedin A, B, C and Icariin which are known mainly for aphrodisiac, antiosteoporosis, anticancer, antioxidant, antiaging, antifatigue and antiviral activities. It is a neglected medicinal plant in Northwestern Himalayan region and may fall in the list of endangered species due to continuous anthropogenic pressures in its native habitats. In this study, we investigated distributional and altitudinal range of this prized species from twenty diverse eco-geographical zones of Kashmir Himalayas for the first time. We also report here its diversity in morphological attributes both in wild and captive cultivation. The species has a very small population size in most of the surveyed habitats with no natural protection. Under cultivation it showed increased plant height (63.09±4.9cm), more number of leaves (95.53±11cm) and flowers (160.76±20cm), indicating importance of high altitude medicinal garden for its immediate &lt;em&gt;ex situ&lt;/em&gt; conservation. Further, the acetocarmine staining and squashing of young anthers confirmed it as a diploid species (2n=12) like other &lt;em&gt;Epimedium&lt;/em&gt; species. Chromosome number and meiotic abnormalities are also reported for the first time in the species. Finally, constant anthropogenic pressures in Northwestern Himalayas demand immediate &lt;em&gt;in situ&lt;/em&gt; and &lt;em&gt;ex situ&lt;/em&gt; conservation programmes for &lt;em&gt;E.elatum&lt;/em&gt;.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;

Cytogenetic variations in eight species of Saussurea DC. (Asteraceae, Cardueae) from Northwest Himalaya

The genus Saussurea comprises many species with highly medicinal, religious or other economical values. The chromosome number in the genus ranges from 2n = 24 to 108, based on x = 12, 13, 16, or 17, but the primary base number is still not clear. The present meiotic study cover 8 species (14 populations) of Saussurea from the Northwest Himalayas, and add new or varied cytotypes, as an attempt to solve the enigmatic cytogenetic variations in the genus. The chromosome numbers in Saussurea auriculata (n = 16) is new to the world, while S. costus (n = 17), S. jacea (n = 17) and S. roylei (n = 17) reveal the varied cytotypes at world level. Besides, S. taraxicifolia (n = 16) is a first ever report for Indian populations. The meiotic studies on different populations reveal a substantial amount of meiotic abnormalities in the form of chromosome stickiness, un-oriented bivalents, cytomixis, laggards, etc. leading to the meiocytes with less (aneuploidy) or more (polyploidy) chromosome numbers. These abnormalities may produce unreduced pollen grains and adversely affect pollen viability. The high number of these meiotic abnormalities may be responsible for the chromosome number variation in the genus.

Meiotic pairing as an indicator of genome composition in polyploid prairie cordgrass (Spartina pectinata Link).

The existence of neopolyploidy in prairie cordgrass (Spartina pectinata Link) has been documented. The neohexaploid was discovered coexisting with tetraploids in central Illinois, and has been reported to exhibit competitiveness in the natural environment. It is hypothesized that the natural tetraploid cytotype produced the hexaploid cytotype via production of unreduced gametes. Meiosis I chromosome pairing was observed in tetraploid (2n = 4x = 40), hexaploid (2n = 6x = 60), and octoploid (2n = 8x = 80) accessions and the percentage of meiotic abnormality was determined. Significant differences in meiotic abnormality exist between tetraploid, hexaploid, and octoploid cytotypes. An elevated incidence of abnormal, predominantly trivalent pairing in the neohexaploid suggests that it may possess homologous chromosomes in sets of three, in contrast to the tetraploid and octoploid cytotypes, which likely possess homologous chromosomes in sets of two. Abnormal chromosome pairing in the hexaploid may result in unequal allocation of chromosomes to daughter cells during later stages of meiosis. Chromosome pairing patterns in tetraploid, hexaploid, and octoploid cytotypes indicate genome compositions of AABB, AAABBB, and AABBA'A'B'B', respectively.

Pollen viability and meiotic abnormalities in brome grasses(Bromus L., Section Ceratochloa) from Argentina

Bromus Section Ceratochloa includes temperate forage species. South American species form a morphologically very variable hexaploid complex (2n = 6x = 42), with a controversial taxonomic classification. Reproductive biology has been studied in several of them, but the number of analyzed plants has seldom been reported. Further investigations might clarify breeding relations and the adequacy of current classifications. Pollen viability and size, which can provide evidence of spontaneous hybridization, were studied in seven accessions (six plants/accession) classified as B. catharticus var. catharticus, var. elata, and var. rupestris; B. parodii; B. bonariensis; B. lithobius; and B. coloratus. Variability was detected among accessions for average pollen viability (54%-82%) and pollen size (15.8%-26.2% n.). Meiotic analyses were performed in a sample of genotypes from five accessions with <70% pollen viability and/or variability in pollen size. Normal and abnormal meiocytes (11.9%-44.5%) were recorded at various meiotic stages in one randomly taken genotype from each sample. Since these cleistogamous species can produce chasmogamous flowers, the analyzed accessions, conserved as species, are apparently of hybrid origin. Segregation in hybrid populations could add to the confusion in taxonomy, affecting both conservation of genetic diversity and efficiency of parental selection in breeding.

Cytological analysis for meiotic patterns in wild rice (Oryza rufipogon Griff.)

The present report explores the chromosomal patterns during meiosis as a fundamental cell division study in wild rice (Oryza rufipogon Griff.). Cytological assays revealed normal meiosis in most cases but in some instances meiotic abnormalities such as weak desynapsis, univalent and quadrivalent formation, translocation, spindle abnormalities and precocious movement of chromosomes were noticed. Interestingly, this wild species also has the bi-nucleoli in first meiotic stages alike the cultivated species of Oryza (O. sativa). The present investigation emphatically addresses the questions of high adaptability of wild rice supported by high pollen fertility for their potential to strong fitness in nature.

Pollen morphology and its relation with meiotic irregularities in ten species of Campuloclinium (Eupatorieae, Asteraceae)

Pollen grains of ten species of Campuloclinium (Eupatorieae, Asteraceae) are described and illustrated using light and scanning electron microscopy. The species included in this study are C. burchelli, C. campuloclinioides, C. chlorolepis, C. hirsutum, C. irwinii, C. macrocephalum, C. megacephalum, C. parvulum, C. purpurascens and C. riedelli. Pollen grains of Campuloclinium are typically radially symmetric, echinate, tectate, oblate-spheroidal to prolate-spheroidal (P/E ratio: 0.94–1.10). Pollen is mostly triaperturate, but tetraaperturate or biaperturate pollen also occurs in some species. The pollen diameter was highly variable ranging from 10.54 µm to 36.18 μm. The significance of the variation in type and size of pollen is discussed in relation to diverse meiotic abnormalities and possible reproductive apomictic processes within the polyploid species.

Cytoembryological evaluation, meiotic behavior and pollen viability of Paspalum notatum tetraploidized plants

Abstract This study evaluated the mode of reproduction, the meiotic behavior and the pollen viability of three tetraploid plants (2n=4x=40) originated from somatic chromosome duplication of Paspalum notatum plants. The plant WKS 3 changed the mode of reproduction after duplication and became apomictic. The plants WKS 63 and WKS 92 confirmed sexual mode of reproduction identical to that of the original genotype. The analyzed plants presented meiotic abnormalities related to tetraploidy, and the chromosome pairing were variable, but it did not hinder the meiotic products, which were characterized by regular tetrads and satisfactory pollen fertility, ranging from 88.7 to 95.7%. Results show that all plants are meiotically stable and that they can be used in intraspecific crosses in the breeding program of Paspalum notatum.

A synopsis of the cytogenetics of the genusPhlomoides(Lamiaceae) in Iran

AbstractThe present study reports the chromosome number and meiotic behavior of 11 populations belonging to four species of Phlomoides (L.) Moench. All populations showed the diploid chromosome number 2n = 2x = 22; consistent with the proposed base number of x = 11. Almost all taxa studied here displayed regular bivalent pairing and chromosome segregation at meiosis. However, meiotic abnormalities observed included varied degree of fragmented chromosomes, laggards and bridge in anaphase I to telophase II, precocious division of centromeres, asynchronous nucleus and cytomixis. In addition, a survey on chromosome counts of different species belonging to the genus Phlomoides throughout the world is presented and the base chromosome numbers and polyploidy levels discussed here.

Use of single nucleotide polymorphism (SNP) arrays and next generation sequencing (NGS) to study the incidence, type and origin of aneuploidy in the human preimplantation embryo

To perform a thorough investigation using a combination of the most advanced technologies available in an effort to decipher the aneuploidy ‘code’ in the human preimplantation embryo. Quantitative assessment and genotyping were undertaken concurrently for human blastocysts using SNP arrays and NGS. Single trophectoderm biopsies were obtained from blastocysts of couples undergoing in vitro fertilization (IVF) with preimplantation genetic diagnosis (PGD) for single gene disorders (SGD) and aneuploidy screening. Karyomapping SNP array (Illumina, USA) was used for PGD of SGD while, NGS via the VeriSeq PGS assay (Illumina) was utilized for comprehensive chromosome screening. Fisher’s exact test (GraphPad Software, USA) was used for statistical analysis. In total, over 19,000 chromosomes were screened in 417 embryos from 75 couples [maternal age: 34.1±0.5 years (mean ± SE)]. At least one chromosomal abnormality was detected in 49.2% (205/417) of the embryos assessed, with 48.3% of the embryos exhibiting only abnormalities of meiotic origin, 40% having only mitotic abnormalities and the remainder of the embryos presenting both types of abnormalities. Notably, maternal meiosis was associated with an equal number of events leading to gain vs. loss of chromosomal material (74 gains vs. 75 losses) and prevailed over paternal meiosis which consisted of events mainly involving loss of chromosomal material (27 losses vs. 1 gain) with almost half of the losses (40.7%) being partial. Of the overall number of aneuploidies detected, 15.7% were determined to be partial with the size of segments gained or lost ranging from 7.8 to 145.6 megabases. Incidences of maternally-derived meiotic errors and overall mitotic errors detected are presented in the table below in relation to maternal age: The incidence of maternal meiotic abnormalities was associated with increasing age, consistent with the higher rates of implantation failure and miscarriage experienced by older women. Mitotic errors, potentially producing mosaicism, were also common. Interestingly, aneuploidy of male meiotic origin was characterized by a predominance of monosomies compared with that of female origin, suggesting a sex-specific difference in the mechanism underlying segregation errors.Tabled 1No. of embryos with meiotic or mitotic errors vs. overall No. of embryos per maternal age groupMaternal Age GroupMaternal Meiotic ErrorsOverall Mitotic Errors< 3445/257 (17.5%)a,b63/257 (24.5%)35-3956/131 (42.7%)a,c34/131 (26.0%)> 4022/29 (75.9%)b,c9/29 (31.0%)Meiotic errors: a difference statistically significant at P<0.0001; b difference statistically significant at P<0.0001; c difference statistically significant at P<0.01.Mitotic errors: No difference detected between the different age groups (P>0.05). Open table in a new tab