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1.
Acta Academiae Medicinae Sinicae ; (6): 142-148, 2022.
Article in Chinese | WPRIM | ID: wpr-927858

ABSTRACT

Aurora kinase A (AURKA),a family member of aurora kinases,is involved in mitotic entry,maturation and separation of centrosome,assembly and stabilization of bipolar spindle,and condensation and separation of chromosome.Studies have demonstrated that AURKA plays a similar role in meiosis,while the specific mechanism and the similarities and differences in its role between meiosis and mitosis remain unclear.Therefore,we reviewed the studies about the localization and activation of AURKA in oocyte meiosis,and compared the role of AURKA in regulating spindle formation,activating spindle assembly checkpoint,and correcting the kinetochore-microtubule attachment between the meiosis of oocytes and the mitosis of somatic cells.This review will lay a theoretical foundation for revealing the mechanism of AURKA in the regulation of cell division and for the clinical research related to cancer and reproduction.


Subject(s)
Humans , Aurora Kinase A/genetics , Cell Cycle Proteins/genetics , Chromosome Segregation , Meiosis , Oocytes
2.
Asian Journal of Andrology ; (6): 572-579, 2021.
Article in English | WPRIM | ID: wpr-922376

ABSTRACT

Programmed DNA double-strand breaks (DSBs) are necessary for meiosis in mammals. A sufficient number of DSBs ensure the normal pairing/synapsis of homologous chromosomes. Abnormal DSB repair undermines meiosis, leading to sterility in mammals. The DSBs that initiate recombination are repaired as crossovers and noncrossovers, and crossovers are required for correct chromosome separation. Thus, the placement, timing, and frequency of crossover formation must be tightly controlled. Importantly, mutations in many genes related to the formation and repair of DSB result in infertility in humans. These mutations cause nonobstructive azoospermia in men, premature ovarian insufficiency and ovarian dysgenesis in women. Here, we have illustrated the formation and repair of DSB in mammals, summarized major factors influencing the formation of DSB and the theories of crossover regulation.


Subject(s)
Animals , Humans , Chromosome Segregation , DNA Breaks, Double-Stranded , DNA Repair/physiology , Mammals/genetics
3.
Asian Journal of Andrology ; (6): 580-589, 2021.
Article in English | WPRIM | ID: wpr-922375

ABSTRACT

The synaptonemal complex (SC) is a meiosis-specific proteinaceous macromolecular structure that assembles between paired homologous chromosomes during meiosis in various eukaryotes. The SC has a highly conserved ultrastructure and plays critical roles in controlling multiple steps in meiotic recombination and crossover formation, ensuring accurate meiotic chromosome segregation. Recent studies in different organisms, facilitated by advances in super-resolution microscopy, have provided insights into the macromolecular structure of the SC, including the internal organization of the meiotic chromosome axis and SC central region, the regulatory pathways that control SC assembly and dynamics, and the biological functions exerted by the SC and its substructures. This review summarizes recent discoveries about how the SC is organized and regulated that help to explain the biological functions associated with this meiosis-specific structure.


Subject(s)
Animals , Chromosome Segregation , Meiosis/physiology , Synaptonemal Complex/physiology
4.
Asian Journal of Andrology ; (6): 562-571, 2021.
Article in English | WPRIM | ID: wpr-922359

ABSTRACT

Repairing DNA double-strand breaks (DSBs) with homologous chromosomes as templates is the hallmark of meiosis. The critical outcome of meiotic homologous recombination is crossovers, which ensure faithful chromosome segregation and promote genetic diversity of progenies. Crossover patterns are tightly controlled and exhibit three characteristics: obligatory crossover, crossover interference, and crossover homeostasis. Aberrant crossover patterns are the leading cause of infertility, miscarriage, and congenital disease. Crossover recombination occurs in the context of meiotic chromosomes, and it is tightly integrated with and regulated by meiotic chromosome structure both locally and globally. Meiotic chromosomes are organized in a loop-axis architecture. Diverse evidence shows that chromosome axis length determines crossover frequency. Interestingly, short chromosomes show different crossover patterns compared to long chromosomes. A high frequency of human embryos are aneuploid, primarily derived from female meiosis errors. Dramatically increased aneuploidy in older women is the well-known "maternal age effect." However, a high frequency of aneuploidy also occurs in young women, derived from crossover maturation inefficiency in human females. In addition, frequency of human aneuploidy also shows other age-dependent alterations. Here, current advances in the understanding of these issues are reviewed, regulation of crossover patterns by meiotic chromosomes are discussed, and issues that remain to be investigated are suggested.


Subject(s)
Humans , Cell Division/physiology , Chromosome Segregation/physiology , Meiosis/genetics , Recombination, Genetic
5.
Acta Academiae Medicinae Sinicae ; (6): 419-424, 2019.
Article in Chinese | WPRIM | ID: wpr-776016

ABSTRACT

The chromosomal aneuploidy in oocytes is one of main causes of abortion and neonatal birth defects.It is mainly due to the premature separation of sister chromatid caused by the loss of Cohesin protein complex and the non-disjunction sister chromatids caused by abnormal microtubule dynamics aneuploidy.As a pathway of protein post-translational modification,SUMO modification(or SUMOylation)involves many physiological regulation processes including cell proliferation,differentiation,apoptosis,and cycle regulation.In the oocytes,SUMOylation can regulate the localization of Cohesin protein complex on the chromosome to affect the chromosomal aneuploidy in oocytes caused by premature separation of sister chromatid.On the other hand,SUMOylation can regulate the microtubule dynamics to affect the chromosomal aneuploidy in oocytes caused by non-disjunction sister chromatids.Therefore,SUMOylation plays an important role in regulating the chromosomal aneuploidy of oocytes;the exact mechanisms via which the SUMOylated substrates affect aneuploidy in oocytes remain unclear.This articles reviews the roles of SUMOylation in premature separation and non-isolated chromatid aneuploidy in oocyte from the effects of SUMOylationon Cohesin protein complex and microtubule dynamics.


Subject(s)
Humans , Aneuploidy , Cell Cycle Proteins , Chromatids , Chromosomal Proteins, Non-Histone , Chromosome Segregation , Microtubules , Oocytes , Cell Biology , Sumoylation
7.
Chinese Medical Journal ; (24): 1209-1214, 2015.
Article in English | WPRIM | ID: wpr-350326

ABSTRACT

<p><b>BACKGROUND</b>In prokaryotic organisms, the mechanism responsible for the accurate partition of newly replicated chromosomes into daughter cells is incompletely understood. Segregation of the replication terminus of the circular prokaryotic chromosome poses special problems that have not previously been addressed. The aim of this study was to investigate the roles of several protein components (MreB, MreC, and MreD) of the prokaryotic cytoskeleton for the faithful transmission of the chromosomal terminus into daughter cells.</p><p><b>METHODS</b>Strain LQ1 (mreB::cat), LQ2 (mreC::cat), and LQ3 (mreD::cat) were constructed using the Red recombination system. LQ11/pLAU53, LQ12/pLAU53, LQ13/pLAU53, LQ14/pLAU53, and LQ15/pLAU53 strains were generated by P1transduction of (tetO) 240 -Gm and (lacO) 240 -Km cassettes from strains IL2 and IL29. Fluorescence microscopy was performed to observe localization pattern of fluorescently-labeled origin and terminus foci in wild-type and mutant cells. SOS induction was monitored as gfp fluorescence from PsulA-gfp in log phase cells grown in Luria-Bertani medium at 37°C by measurement of emission at 525 nm with excitation at 470 nm in a microplate fluorescence reader.</p><p><b>RESULTS</b>Mutational deletion of the mreB, mreC, or mreD genes was associated with selective loss of the terminus region in approximately 40% of the cells within growing cultures. This was accompanied by significant induction of the SOS DNA damage response, suggesting that deletion of terminus sequences may have occurred by chromosomal cleavage, presumably caused by ingrowth of the division septum prior to segregation of the replicated terminal.</p><p><b>CONCLUSIONS</b>These results imply a role for the MreBCD cytoskeleton in the resolution of the final products of terminus replication and/or in the specific movement of newly replicated termini away from midcell prior to completion of septal ingrowth. This would identify a previously unrecognized stage in the overall process of chromosome segregation.</p>


Subject(s)
Chromosome Segregation , Genetics , Physiology , Cytoskeleton , Metabolism , Escherichia coli , Genetics , Metabolism
8.
Electron. j. biotechnol ; 17(1): 2-2, Jan. 2014. ilus, tab
Article in English | LILACS | ID: lil-706516

ABSTRACT

Background The quality of wheat grain depends on several characteristics, among which the composition of high molecular weight glutenin subunits, encoded by Glu-1 loci, are the most important. Application of biotechnological tools to accelerate the attainment of homozygous lines may influence the proportion of segregated genotypes. The objective was to determine, whether the selection pressure generated by the methods based on in vitro cultures, may cause a loss of genotypes with desirable Glu-1 alleles. Results Homozygous lines were derived from six winter wheat crosses by pollination with maize (DH-MP), anther culture (DH-AC) and single seed descent (SSD) technique. Androgenetically-derived plants that originated from the same callus were examined before chromosome doubling using allele-specific and microsatellite markers. It was found that segregation distortion in SSD and DH-MP populations occurred only in one case, whereas in anther-derived lines they were observed in five out of six analyzed combinations. Conclusions Segregation distortion in DH-AC populations was caused by the development of more than one plant of the same genotype from one callus. This distortion was minimized if only one plant per callus was included in the population. Selection of haploid wheat plants before chromosome doubling based on allele-specific markers allows us to choose genotypes that possess desirable Glu-1 alleles and to reduce the number of plants in the next steps of DH production. The SSD technique appeared to be the most advantageous in terms of Mendelian segregation, thus the occurrence of residual heterozygosity can be minimized by continuous selfing beyond the F6 generation.


Subject(s)
Triticum/genetics , Chromosome Segregation , Seeds/genetics , In Vitro Techniques , Microsatellite Repeats , Zea mays , Alleles , Genotype , Glutens/analysis , Homozygote
9.
Journal of Zhejiang University. Medical sciences ; (6): 446-450, 2011.
Article in Chinese | WPRIM | ID: wpr-247231

ABSTRACT

BubR1 gene is a homologue of the mitotic checkpoint gene Mad3 in budding yeast which is highly conserved in mammalian. BubR1 protein is a key component mediating spindle assembly checkpoint activation. BubR1 safeguards accurate chromosome segregation during cell division by monitoring kinetochore-microtubule attachments and kinetochore tension. There is a dose-dependent effect between the level of BubR1 expression and the function of spindle assembly checkpoint. BubR1-deficient would lead to mitotic progression with compromised spindle assembly checkpoint because cells become progressively aneuploid. Recently, it has been reported that BubR1 also plays important roles in meiotic, DNA damage response, cancer, infertility, and early aging. This review briefly summarizes the current progresses in studies of BubR1 function.


Subject(s)
Cell Cycle Proteins , Genetics , Metabolism , Physiology , Chromosome Segregation , Genetics , Physiology , Kinetochores , Metabolism , Physiology , Mitosis , Genetics , Physiology , Protein Serine-Threonine Kinases , Genetics , Metabolism , Physiology , Saccharomycetales , Genetics , Physiology , Spindle Apparatus , Genetics , Metabolism , Physiology
10.
The Korean Journal of Laboratory Medicine ; : 49-53, 2011.
Article in English | WPRIM | ID: wpr-30861

ABSTRACT

Miller-Dieker syndrome involves a severe type of lissencephaly, which is caused by defects in the lissencephaly gene (LIS1). We report the case of a female infant with der(17)t(12;17)(q24.33;p13.3)pat caused by an unbalanced segregation of the parental balanced translocation of 17p with other chromosomes. The proband presented with facial dysmorphism, arthrogryposis, and intrauterine growth retardation. Most cases of Miller-Dieker syndrome have a de novo deletion involving 17p13.3. When Miller-Dieker syndrome is caused by an unbalanced translocation, mild-to-severe phenotypes occur according to the extension of the involved partner chromosome. However, a pure partial monosomy derived from a paternal balanced translocation is relatively rare. In this case, the submicroscopic cryptic deletion in the proband was initially elucidated by FISH, and karyotype analysis did not reveal additional chromosome abnormalities such as translocation. However, a family history of recurrent pregnancy abnormalities strongly suggested familial translocation. Sequential G-banding and FISH analysis of the father's chromosomes showed that the segment of 17p13.3-->pter was attached to the 12qter. Thus, we report a case that showed resemblance to the findings in cases of a nearly pure 17p deletion, derived from t(12;17), and delineated by whole genome array comparative genomic hybridization (CGH). If such cases are incorrectly diagnosed as Miller-Dieker syndrome caused by de novo 17p13.3 deletion, the resultant improper genetic counseling may make it difficult to exactly predict the potential risk of recurrent lissencephaly for successive pregnancies.


Subject(s)
Adult , Female , Humans , Infant, Newborn , Male , Abnormalities, Multiple/genetics , Brain/abnormalities , Chromosome Banding , Chromosome Segregation , Chromosomes, Human, Pair 12 , Chromosomes, Human, Pair 17 , Classical Lissencephalies and Subcortical Band Heterotopias/diagnosis , Gene Deletion , In Situ Hybridization, Fluorescence , Karyotyping , Magnetic Resonance Imaging , Phenotype , Risk , Translocation, Genetic
11.
Clinical and Experimental Reproductive Medicine ; : 68-74, 2011.
Article in English | WPRIM | ID: wpr-70207

ABSTRACT

OBJECTIVE: Previously, we found that oocyte specific homeobox (Obox) 4 plays significant role in completion of meiosis specifically at meiosis I-meiosis II (MI-MII) transition. The purpose of this study was to determine the mechanism of action of Obox4 in oocyte maturation by evaluating downstream signal networking. METHODS: The Obox4 dsRNA was prepared by in vitro transcription and microinjected into the cytoplasm of germinal vesicle oocytes followed by in vitro maturation in the presence or absence of 0.2 mM 3-isobutyl-1-metyl-xanthine. Total RNA was extracted from 200 oocytes of each group using a PicoPure RNA isolation kit then amplified two-rounds. The probe hybridization and data analysis were used by Affymetrix GeneChip(R) Mouse Genome 430 2.0 array and GenPlex 3.0 (ISTECH, Korea) software, respectively. RESULTS: Total 424 genes were up (n=80) and down (n=344) regulated after Obox4 RNA interference (RNAi). Genes mainly related to metabolic pathways and mitogen-activated protein kinase (MAPK) signaling pathway was changed. Among the protein kinase C (PKC) isoforms, PKC-alpha, beta, gamma were down-regulated and especially the MAPK signaling pathway PKC-gamma was dramatically decreased by Obox4 RNAi. In the cell cycle pathway, we evaluated the expression of genes involved in regulation of chromosome separation, and found that these genes were down-regulated. It may cause the aberrant chromosome segregation during MI-MII transition. CONCLUSION: From the results of this study, it is concluded that Obox4 is important upstream regulator of the PKC and anaphase-promoting complex action for maintaining intact germinal vesicle.


Subject(s)
Animals , Mice , Cell Cycle , Chimera , Chromosome Segregation , Cytoplasm , Gene Expression , Genes, Homeobox , Genome , Meiosis , Metabolic Networks and Pathways , Microarray Analysis , Oocytes , Protein Isoforms , Protein Kinase C , Protein Kinases , RNA , RNA Interference , Statistics as Topic , Ubiquitin-Protein Ligase Complexes
12.
Rio de Janeiro; s.n; 2009. 105 p. ilus, tab.
Thesis in Portuguese | LILACS, BBO | ID: lil-553182

ABSTRACT

Um estudo sugere que o fenótipo da periodontite agressiva localizada está ligado a região 1q25. O objetivo do presente estudo foi aperfeiçoar o mapeamento genético da periodontite agressiva na região cromossômica supracitada em famílias clinicamente bem caracterizadas segregando a doença. A hipótese deste estudo é que variações genéticas localizadas no cromossomo 1 entre as regiões 1q 24.2 e 1q 31.3 contribuem para o fenótipo da periodontite agressiva. Como objetivos específicos, determinamos o modo de herança da periodontite agressiva através de análise de segregação, e verificamos a existência de ligação e/ou associação entre a região 1q 24.2-1q 31.3 e a periodontite agressiva. A análise de segregação foi executada no programa SEGREG do pacote SAGE versão 5.4.2 com base nos dados dos pedigrees das primeiras 74 famílias recrutadas neste estudo, totalizando 475 indivíduos (média de 6.4 indivíduos por família) de origem geográfica similar. Assumiu-se a herança Mendeliana como um locus autossômico com 2 alelos A e B, onde o alelo A estava associado ao fenótipo relevante. Cinco modos de transmissão (não homogêneo, Mendeliano homogêneo, homogêneo geral, semigeral, heterogêneo geral) foram testados assumindo que a prevalência da periodontite agressiva é de 1% sob o Equilíbrio de Hardy-Weinberg. Foram coletadas amostras de saliva de 54 das 74 famílias recrutadas, totalizando 371 amostras de saliva para a extração do DNA genômico. 21 polimorfismos de um único nucleotídeo (SNPs) foram selecionados dentro da região proposta e analisados por reação em cadeia da polimerase (PCR). Os genótipos foram obtidos pelo método TaqMan. A análise não paramétrica de ligação familial foi executada com o Programa Merlin. As detecções de transmissão (associação) foram executadas com os programas FBAT e PLINK. O modo de herança mais adequado para cada teste de susceptibilidade dos alelos executado foi o modelo semigeral (p=0,31)...


It has been suggested that the localized aggressive periodontitis phenotype is linked to the region 1q25. The aim of this study was to fine map the chromosome interval suggested as containing a localized aggressive periodontitis locus in clinically well characterized group of families segregating aggressive periodontitis. The hypothesis of this study is that genetic variation located between 1q24.2 to 1q31.3 contributes to the phenotype of aggressive periodontitis. As specific aims, we evaluated the inheritance mode of aggressive periodontitis performing segregation analysis and, we tested the presence of linkage and or association between the target region of chromosome 1 and aggressive periodontitis. Segregation analysis was performed in pedigree data from the first 74 families, comprised of 475 individuals (average of 6.4 individuals per family) with similar geographic origin by the use of the SEGREG program of SAGE v.5.4.2. Mendelian inheritance was assumed to be through an autosomal locus with two alleles A and B, where the A allele was associated with the relevant phenotype. Five inheritance modes (homogeneous no transmission, homogeneous Mendelian transmission, homogeneous general transmission, semi-general transmission, heterogeneous general transmission) were tested assuming the prevalence of aggressive periodontitis as 1% and no deviations from Hardy-Weinberg equilibrium. Saliva samples were collected from 54 families, 371 individuals and DNA was extracted from this biological material. Twenty-one single nucleotide polymorphisms (SNPs) were selected and analyzed by standard polymerase chain reaction. The genotypes were obtained by the TaqMan method. The non-parametric analysis of familial linkage was performed with Merlin software. Analyses of transmission detection (association) were performed by FBAT and PLINK programs. The most parsimonious mode of inheritance in each susceptibility type tested was the semi-general transmission mode (p=0,31)...


Subject(s)
Humans , Chromosome Segregation , Aggressive Periodontitis/genetics , Polymorphism, Genetic/genetics , Chromosome Mapping , Linkage Disequilibrium/genetics , Genetic Association Studies/methods , Multifactorial Inheritance/genetics
13.
J Environ Biol ; 2008 Jul; 29(4): 555-7
Article in English | IMSEAR | ID: sea-113711

ABSTRACT

In the course of quantitative trait loci (QTL) analysis of the back cross (BC1) families of olive flounder (Paralichtys olivaceus), we observed significant segregation distortion at a microsatellite marker Poli9-58TUF in two crosses of informative progenies. The family 1 of the random BC1 progenies derived from a cross between a F1 male genotype (A/B) and a F1's female parent genotype (A/C) and the family 2 (A/C x A/C) displayed a strong bias in the locus from the Mendelian inheritance by the elimination of homozygous A/A genotype. The deleterious roles of the AA genotypes are suggested during the metamorphosis and it implies that the parents of these families carried a recessive gene or genes hampering development at an early stage because the offspring of the double heterozygote parents show the reduction in frequency or elimination of one homozygous class, which is an evidence for linkage between the genetic marker and gene(s) with recessive deleterious alleles. This data support a hypothesis that the region contains a recessive lethal gene or genes.


Subject(s)
Alleles , Animals , Chromosome Segregation/genetics , Crosses, Genetic , Female , Flounder/genetics , Genetic Markers , Genotype , Heterozygote , Homozygote , Inbreeding , Genetic Linkage , Male , Microsatellite Repeats/genetics , Quantitative Trait Loci/genetics
14.
Genet. mol. res. (Online) ; 7(2): 424-432, 2008. tab, ilus
Article in English | LILACS | ID: lil-640996

ABSTRACT

Microsporogenesis in an interspecific Brachiaria hybrid, grown in the field under natural environmental conditions in Brazilian savannas, was analyzed in three distinct years of collection. Several types of meiotic abnormalities were recorded during those three years, but varied in type and frequency depending on the year. The average temperature and rainfall 15 days before collection was unusually high in those years. The percentage of abnormal meiocytes recorded was 62% in 2001, 73% in 2004, and 77% in 2005. The abnormalities observed during microsporogenesis compromised pollen viability by generating unbalanced gametes or affecting nucleolus organization. The environmental conditions under which the hybrid was growing could have affected the genetic control of meiosis. More detailed studies, under controlled conditions, are necessary to better understand the effects of environmental factors on Brachiaria microsporogenesis hybrids.


Subject(s)
Brachiaria/genetics , Meiosis/genetics , Brachiaria/cytology , Chromosome Segregation , Chromosomes, Plant/genetics , Hybridization, Genetic , Temperature
15.
Genet. mol. res. (Online) ; 6(3): 691-706, 2007. ilus, tab
Article in English | LILACS | ID: lil-498900

ABSTRACT

The present study describes a new set of 61 polymorphic microsatellite markers for beans and the construction of a genetic map using the BAT93 x Jalo EEP558 (BJ) population for the purpose of developing a reference linkage map for common bean (Phaseolus vulgaris). The main objectives were to integrate new microsatellites on the existing framework map of the BJ population, and to develop the first linkage map for the BJ population based exclusively on microsatellites. Of the total of 264 microsatellites evaluated for polymorphism, 42.8% showed polymorphism between the genitors. An integrated map was created totaling 199 mapped markers in 13 linkage groups, with an observed length of 1358 cM and a mean distance between markers of 7.23 cM. For the map constructed exclusively with microsatellites, 106 markers were placed in 12 groups with a total length of 606.8 cM and average distance of 6.8 cM. Linkage group designation and marker order for BM microsatellites generally agreed with previous mapping, while the new microsatellites were well distributed across the genome, corroborating the utility of the BJ population for a reference map. The extensive use of the microsatellites and the availability of a reference map can help in the development of other genetic maps for common bean through the transfer of information of marker order and linkage, which will allow comparative analysis and map integration, especially for future quantitative trait loci and association mapping studies.


Subject(s)
Chromosome Mapping , Hybridization, Genetic , Phaseolus/genetics , Microsatellite Repeats/genetics , Chromosome Segregation , Chromosomes, Plant/metabolism , Genetic Linkage , Genetic Markers , Minisatellite Repeats , Polymorphism, Genetic
16.
Genet. mol. res. (Online) ; 6(3): 634-642, 2007. ilus, tab
Article in English | LILACS | ID: lil-498907

ABSTRACT

The heterokaryotic and vegetative diploid phases of Colletotrichum lindemuthianum are described using nutritional and biochemical markers. Nitrate non-utilizing mutants (nit), derived from R2047, R89, R73, R65, and R23 isolates, were paired in all possible combinations to obtain heterokaryons. Although pairings R2047/R89, R2047/R73, R65/R73, and R73/R23 showed complete vegetative incompatibility, prototrophic heterokaryons were obtained from pairings R2047/R65, R2047/R23, R65/R89, R65/R23, R73/R89, R89/R23, R2047/R2047, R65/R65, R89/R89, R73/R73, and R23/R23. Heterokaryons gave rise to spontaneous mitotic segregants which carried markers corresponding to one or the other of the parental strains. Heterokaryons spontaneously produced prototrophic fast-growing sectors too, characterized as diploid segregants. Diploids would be expected to yield auxotrophic segregants following haploidization in basal medium or in the presence of benomyl. Parental haploid segregants were in fact recovered from diploid colonies growing in basal medium and basal medium containing the haploidizing agent. Although barriers to the formation of heterokaryons in some crosses were detected, the results demonstrate the occurrence of parasexuality among vegetative compatible mutants of C. lindemuthianum.


Subject(s)
Chromosome Segregation , Colletotrichum/cytology , Diploidy , Nitrates/metabolism , Phaseolus/microbiology , Colletotrichum/enzymology , Esterases/metabolism , Haploidy , Hyphae/cytology , Mutation/genetics , Cell Nucleus/metabolism , Phenotype
17.
Genet. mol. res. (Online) ; 6(3): 607-615, 2007. ilus, tab, graf
Article in English | LILACS | ID: lil-498911

ABSTRACT

We examined the capacity of strains of Glomerella cin-gulata f. sp phaseoli fungus (Colletotrichum lindemuthianum sexual stage) to form recombinants, using random amplified polymorphic DNA (RAPD). Crosses of all possible combinations between strains 40, 42, 20, 21, 22, 23, 24, 25, and 26 were made on Petri dishes using M3 culture medium. The 42 x 21 cross produced the largest number of perithecia and five asci; the respective ascospores were isolated. RAPD analysis was performed on the parents and descendants. The 62 polymorphic RAPD bands obtained were used to assess the genetic similarity using the method of Sorence and Dice and clustering analysis in the form of a dendrogram by the UPGMA method. The RAPD markers allowed identification of recombinants from the cross between strains 42 and 21 of G. cingulata f. sp phaseoli and 40 ascospores presented 63 and 49% genetic similarity with parents 2 (strain 42) and 1 (strain 21), respectively.


Subject(s)
Crosses, Genetic , Phyllachorales/physiology , Random Amplified Polymorphic DNA Technique/methods , Chromosome Segregation , Confidence Intervals , Clusterin/analysis , Genetic Markers , Phylogeny
18.
Genet. mol. res. (Online) ; 6(4): 1107-1117, 2007. ilus, tab
Article in English | LILACS | ID: lil-520038

ABSTRACT

Three sexual interspecific hybrids of Brachiaria (HBGC076, HBGC009, and HBGC014) resulting from crosses between B. ruziziensis (female genitor) and B. decumbens and B. brizantha (male genitors) produced by Embrapa Beef Cattle in the 1980s were cytologically analyzed by conventional methods for meiotic studies. The cytogenetic analysis showed the occurrence of common meiotic abnormalities among them. The most frequent abnormalities were those related to irregular chromosome segregation due to polyploidy. Other abnormalities, such as chromosome stickiness, absence of cytokinesis, irregular cytokinesis, abnormal spindle orientation, and abnormal nucleolus disintegration, were found in the three hybrids, while, chromosome disintegration was detected only in HBGC014. All the abnormalities, except for abnormal nucleolus disintegration, can cause unbalanced gamete formation, leading to pollen sterility. Multivalent chromosome association at diakinesis revealed genome affinity between the two parental species in the hybrids, suggesting some possibility for gene introgression. Presently, the Brachiaria breeding program has the objective of releasing, primarily, apomictic hybrids as new cultivars since they do not segregate but preserve the genetic makeup indefinitely. Besides, they result in homogeneous pastures which are easier to manage. The sexual hybrids, however, are paramount in the breeding program: they work as ‘bridges’ to introgress traits of interest into the apomictic genotypes. The cytogenetic analyses of these three hybrids substantiate their maintenance in the breeding program due to low frequency of meiotic abnormalities, complemented by interesting agronomic traits. They may be used in crosses to generate new cultivars in the future.


Subject(s)
Brachiaria/genetics , Hybridization, Genetic , Breeding , Brachiaria/cytology , Chromosome Segregation , Chromosomes, Plant , Cytokinesis , Gametogenesis , Micronuclei, Chromosome-Defective , Meiosis/genetics , Polyploidy
19.
J Biosci ; 2006 Dec; 31(5): 629-37
Article in English | IMSEAR | ID: sea-110959

ABSTRACT

Spontaneous intercellular chromatin migration/cytomixis was observed to occur in the pollen mother cells (PMCs) of the Chlorophytum comosum for the first time. The migration through cytomictic channels was more pronounced in meiosis-I and very rare in meiosis-II. The process was associated with erratic meiosis, which was characterized by defects in chromosome organization and segregation. Cytomixis was more intense in the month of April than in July and consequently the frequency of meiotic irregularities was much more pronounced during the month of April. As a consequence of abnormal meiosis, fertility was drastically reduced resulting in meager seed efficiency of 17% only. Recombination system also does not guarantee the release of sufficient variability. We view the phenomenon of cytomixis as genetically controlled mechanism involving meiotic genes and operating through signal transduction pathway triggered by the environmental stimuli. The evolutionary significance and tenable hypothesis in the backdrop of existing literature is also proposed.


Subject(s)
Asparagaceae/cytology , Chromatin/metabolism , Chromosome Segregation/physiology , Meiosis/physiology , Pollen Tube/cytology , Reproduction , Seasons , Seeds/cytology
20.
Braz. j. biol ; 66(1a): 151-159, Feb. 2006. ilus, tab, graf
Article in English | LILACS | ID: lil-426277

ABSTRACT

Estudos reprodutivos foram realizados em acessos brasileiros de poaia, Cephaelis ipecacuanha. O comportamento meiótico foi estudado usando a técnica de esmagamento. Foi observada segregação irregular de cromossomos durante meiose I e II, muitos grupos de cromossomos em telófase II, micronúcleos, divisão incorreta do citoplasma, citocinese incompleta e produtos pós-meióticos anômalos, principalmente políades. A média do índice meiótico foi inferior a 72%. A viabilidade polínica foi analisada utilizando-se solução de Alexander e a percentagem de pólen viável variou entre as formas florais, brevistila e longistila (85,3% a 93,1%), e entre as diferentes localidades (82,5% a 92,6%) analisadas. O tamanho do pólen variou entre viáveis e inviáveis, e entre os inviáveis vazios e contraídos. Em seu habitat natural, a poaia apresenta propagação por multiplicação vegetativa, mas a reprodução sexuada parece ser tão importante para essa espécie quanto a propagação vegetativa.


Subject(s)
Cephaelis/physiology , Chromosome Segregation/genetics , Chromosomes, Plant/genetics , Meiosis/physiology , Pollen/anatomy & histology , Meiosis/genetics , Reproduction/genetics , Reproduction/physiology
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