• Journal of The Korean Association For Science Education
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• v.30 no.7
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• pp.908-919
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• 2010

The objectives of this study were to investigate what kind of background concepts is necessary to help that high school students easily understand meiosis and to find out how these background concepts affect students' understanding of meiosis. To achieve these objectives, first this study surveyed meiosis background concepts that high school teachers think. Based on 8 background concepts - nuclear phases, chromosome, mitosis, reproduction, gamete, gene, mother/daughter cell - of previous survey, the questionnaire was made for the 10th(724) and 11th(862) grade students and then was analyzed for the effect of meiosis background concepts on the high school students' understanding of meiosis. Results of the analysis revealed that the influential background concepts are as follow; cell cycle, chromosome in the advanced level, mother/daughter cell, mitosis, chromosome, nuclear phases in the intermediate level, mother/daughter cell, nuclear phases, gene in the low level. And the achievement according to item types was differed not by meiosis achievement, but by each background concepts.

• Reproductive and Developmental Biology
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• v.29 no.4
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• pp.223-227
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• 2005

In vitro maturation of porcine immature cumulus-enclosed oocytes can be enhanced by co-incubation with spermatozoa even before fertilization. The aim of this study was to determine whether the addition of spermatozoa into the culture medium can stimulate the meiosis resumption of porcine cumulus-enclosed oocytes arrested at germinal vesicle (GV). Cumulus-enclosed oocytes (CEOs) were collected from follicles of 3 to 5mm diameter. Porcine CEOs were cultured in tissue culture medium containing various meiosis inhibitors and spermatozoa. Oocytes were examined for evidence of GV and GV breakdown after 24 h culture. After 24 h culture $43.8\%$ of oocytes cultured in only TCM 199 remained at GV stage whereas $56.2\%$ of oocytes were able to resume meiosis. When porcine CEOs were cultured in the medium with meiosis inhibitor such as, dibutyryl cAMP (dbcAMP) and forskolin (Fo), more than $90\%$ of oocytes were not able to resume meiosis. However, co-culture of porcine CEOs with spermatozoa was able to overcome the inhibitory effect of dbcAMP and Fo. Irrespective of the presence of 3-isobutyl-1-methylxanthine (IBMX), no difference was observed in the proportion of oocyte reached germinal vesicle breakdown (GVBD). The present study suggests that dbcAMP and Fo prevent the spontaneous maturation of competent oocyte in culture after isolation from follicles and that mammalian spermatozoa contain a substance(s) that improves meiosis resumption in vitro of porcine cumulus-enclosed oocytes.

• Korean Journal of Poultry Science
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• v.15 no.2
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• pp.67-71
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• 1988

In order to induce the diploid gamete(ovum) under suppression of meiosis in oogenesis for production of polyploid chicken. this experiment checked meiosis time. through regular ovulation and response of inhibitor (Tri-ethylen Melamine) to meiosis. The results obtained was follows; ＊Meiosis of oogenesis was 2-4 hours before ovulation. ＊Response of inhibitor to meiosis was effective at 0.3mg triethylen melamine per kg body weight. ＊Fertility was highly decreased by influence from inhibitor. ＊66% of fertilized eggs was triploid(3n) through fertilization induced diploid ovum (2n) with normal sperm(n).

• Journal of Plant Biology
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• v.30 no.4
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• pp.225-247
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• 1987

Meiosis and postmeiotic mitosis in Boletus rubinellus were examined ultrastructurally. Meriosis occurred at the apex of the basidium. A sausage-shaped spindle pole body(SPB) was observed along with the presence of synaptonemal complexes during pachytene and a diglobular SPB was present on late pachytene or diplotene nuclei. During metaphase I, the monoglobular SPB at the spindle pole was surrounded bya membrane and the nuclear enveloope was discontinuous. At anaphase I, the chromosomes became better defined and formed a central spindle. The nucleolus was extruded from the nucleus. During anaphase I, the SPB was excluded from the chromosomal region by a membrane and both poles were fully separated to opposite sides of the basidial wall. In meiosis II, the two nuclei divided synchronously and the spindles were parallel. The spindles were smaller than in meiosis I, while the SPB was approximately the same size as that of the similar stage in meiosis I. During anaphasetelophase II, the SPB was surrounded by a cap of endoplasmic reticulum (ER) that delimited it from the spindle. The postmeiotic interphase nuclei migrated to the mid-region of the basidium before migration to the spores. The SPB at this stage was diglobular. A postmeiotic mitosis occurred within the basidiospore, and the plane of the spindle was obique to the long axis of the spore. The spindle and SPB were smaller than at meiosis I and there were fewer nonchromosomal microtubules. At anaphase, the nucleolus was present inside the nuclear envelope but lateral to the spindle.

• BMB Reports
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• v.52 no.10
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• pp.607-612
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• 2019

During meiosis, programmed double-strand breaks (DSBs) are repaired via recombination pathways that are required for faithful chromosomal segregation and genetic diversity. In meiotic progression, the non-homologous end joining (NHEJ) pathway is suppressed and instead meiotic recombination initiated by nucleolytic resection of DSB ends is the major pathway employed. This requires diverse recombinase proteins and regulatory factors involved in the formation of crossovers (COs) and non-crossovers (NCOs). In mitosis, spontaneous DSBs occurring at the G1 phase are predominantly repaired via NHEJ, mediating the joining of DNA ends. The Ku complex binds to these DSB ends, inhibiting additional DSB resection and mediating end joining with Dnl4, Lif1, and Nej1, which join the Ku complex and DSB ends. Here, we report the role of the Ku complex in DSB repair using a physical analysis of recombination in Saccharomyces cerevisiae during meiosis. We found that the Ku complex is not essential for meiotic progression, DSB formation, joint molecule formation, or CO/NCO formation during normal meiosis. Surprisingly, in the absence of the Ku complex and functional Mre11-Rad50-Xrs2 (MRX) complex, a large portion of meiotic DSBs was repaired via the recombination pathway to form COs and NCOs. Our data suggested that Ku complex prevents meiotic recombination in the elimination of MRX activity.

• Journal of Microbiology and Biotechnology
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• v.27 no.6
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• pp.1198-1203
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• 2017

Hrr25, a casein kinase $1{\delta}/{\varepsilon}$ homolog in budding yeast, is essential to set up mono-orientation of sister kinetochores during meiosis. Hrr25 kinase activity coordinates sister chromatid cohesion via cohesin phosphorylation. Here, we investigated the prophase role of Hrr25 using the auxin-inducible degron system and by ectopic expression of Hrr25 during yeast meiosis. Hrr25 mediates nuclear division in meiosis I but does not affect DNA replication. We also found that initiation of meiotic double-strand breaks as well as joint molecule formation were normal in HRR25-deficient cells. Thus, Hrr25 is essential for termination of meiotic division but not homologous recombination.

• Journal of Life Science
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• v.11 no.4
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• pp.354-361
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• 2001

Chromosomal characteristics of New Zealane White rabbit was studied at meiosis and mitosis. The meiotic chromosomal preparations were mad with the modified air-drying method and karyotype analysis was performed with the G-banding technique, using isolated mitotic metapase chromosomes of the New Zealand White rabbit. Chromosomes, sex vesicles and centromeres could be classified in the zygotene and the pachytene of the meiosis I. The hair-like processes projecting laterally from the axes of bivalent chromosomes at the mid-to-late pachytene were observed and made the appearance of the lampbrush chromosome structure. Chromosomes could be classified onthe basis of the numbers and locations of chiasma in the diakinesis. Twenty-one autosomal bivalents and a single unequal terminally associated X-Y bivalent were observe during the late prophase and the metaphase of the meiosis I. Most of the bivalent types observed in the New Zealand White rabbit spermatrocytes were 1CH, 1TAl, and 2TA bivalents. The mean chiasma frequency(CF) of the male New Zealand White rabbit was 30.2 and it was found that the CF value tended to decrease through diakinesis and the metaphase I. The karyotype of the New Zealand White rabbit was a male chromosome number of 44(2n=44) comprising 8 pairs of metacentric, 9 pairs of submetacentric, 4 pairs o acrocentric autosomes, metacentric X chromosome and acrocentric Y chromosome.

• Korean Journal of Medicinal Crop Science
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• v.14 no.6
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• pp.354-359
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• 2006

Chromosome analysis using mitosis, meiosis and bicolor FISH were carried out in Bupleurum latissimum Nakai, which is one of the endemic plants in Ulleung island of korea. The somatic methaphase chromosomes number of this plant was 2n = 2x = 16 and the chromosome complements consisted of six pairs of metacentrics and two pairs of submetacentrics. The size of chromosomes ranged 2.40${\sim}$4.20 ${\mu}$m and NOR (nucleolus organizer region) chromosome did not observed using conventional staining. In meiosis chromosomes, metaphase-I and anaphase-I were observed. Metaphase-I anaphase-I showed 8 bivalents and chromosomes migration to make two daughter cells. Using bicolor FISH, one pair of 5S and 45S rDNA signals were detected on the centromeric region of chromosome 3 and the end of short of chromosome 2,respectively. We also observed the NOR using 45S rDNA probe.

• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.1026-1035
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• 2015

Condensin is not only responsible for chromosome condensation, but is also involved in double-strand break (DSB) processing in the cell cycle. During meiosis, the condensin complex serves as a component of the meiotic chromosome axis, and mediates both proper assembly of the synaptonemal complex and DSB repair, in order to ensure proper homologous chromosome segregation. Here, we used the budding yeast Saccharomyces cerevisiae to show that condensin participates in a variety of chromosome organization processes and exhibits crucial molecular functions that contribute to meiotic recombination during meiotic prophase I. We demonstrate that Ycs4 is required for efficient DSB formation and establishing homolog bias at the early stage of meiotic prophase I, which allows efficient formation of interhomolog recombination products. In the Ycs4 meiosis-specific allele (ycs4S), interhomolog products were formed at substantial levels, but with the same reduction in crossovers and noncrossovers. We further show that, in prophase chromosomal events, ycs4S relieved the defects in the progression of recombination interactions induced as a result of the absence of Rec8. These results suggest that condensin is a crucial coordinator of the recombination process and chromosome organization during meiosis.

• Journal of Plant Biotechnology
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• v.45 no.1
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• pp.1-8
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• 2018

Meiosis is a specialized cell division, essential in most reproducing organisms to halve the number of chromosomes, thereby enabling the restoration of ploidy levels during fertilization. A key step in meiosis is homologous recombination, which promotes homologous pairing and generates crossovers (COs) to connect homologous chromosomes until their separation at anaphase I. These CO sites, seen cytologically as chiasmata, represent a reciprocal exchange of genetic information between two homologous non-sister chromatids. RAD51, the eukaryotic homolog of the bacterial RecA recombinase, plays a central role in homologous recombination (HR) in yeast and animals. Loss of RAD51 function causes lethality in the flowering plant, Arabidopsis thaliana, suggesting that RAD51 has a meiotic stage-specific function that is different from homologous pairing activity.