四倍体鲫鲤、三倍体湘云鲫染色体减数分裂观察

用精巢细胞直接制片法观察了异源四倍体鲫鲤、三倍体湘云鲫和二倍体红鲫、湘江野鲤精母细胞染色体第一次减数分裂中期配对情况 ;作为对照 ,观察了上述四种鱼肾细胞的有丝分裂中期染色体。在精母细胞第一次减数分裂中 ,异源四倍体鲫鲤同源染色体两两配对 ,形成 10 0个二价体 ,没有观察到单价体、三价体和四价体 ;三倍体湘云鲫精母细胞形成 5 0个二价体和 5 0个单价体 ;红鲫和湘江野鲤精母细胞分别形成 5 0个二价体。肾细胞检测表明异源四倍体的染色体数目为 4n =2 0 0 ;湘云鲫为 3n =15 0 ;红鲫和湘江野鲤分别为 2n =10 0。减数分裂时染色体分布情况与肾细胞染色体检测结果相吻合。具有四套染色体的异源四倍体鲫鲤在减数分裂中只形成 10 0个二价体 ,而不形成 2 5个四价体或其它形式 ,为产生稳定一致的二倍体配子提供了重要的遗传保障 ,也为人工培育的异源四倍体鲫鲤群体能够世世代代自身繁衍下去提供了重要的遗传学证据。三倍体湘云鲫在减数分裂过程中出现二价体、单价体共存 ,同源染色体在配对和分离中出现紊乱 ,导致非整倍体生殖细胞的产生 ,为湘云鲫的不育性提供了染色体水平上的证据     

FISH分析栽培高粱×拟高粱、甜高粱×拟高粱的染色体行为

采用荧光原位杂交技术对45S rDNA在栽培高粱×拟高粱、甜高粱×拟高粱F1的有丝分裂和减数分裂染色体进行定位研究。在有丝分裂中期染色体上2个杂种分别检测到2个杂交信号, 在减数分裂粗线期、终变期、中期Ⅰ染色体上45S rDNA位于一个二价体上, 说明这两个杂种携带45S rDNA的染色体为同源染色体。根据45S rDNA位点随细胞减数分裂过程的位置变化, 表明这两个杂种染色体配对行为正常, 平均构型为2n=2x=20(10Ⅱ), 证明45S rDNA可作为染色体的一个识别指标间接地观察细胞减数分裂过程染色体的变化行为。     

秤锤树的核型研究及其减数分裂过程的观察

观察研究了秤锤树有丝分裂和减数分裂的细胞学特征。秤锤树核型为2n=2x=24=4m 7sm(2SAT) 1st,属于较为原始的2A型。有丝分裂间期核为复杂染色中心型,前期出现B染色体,中期染色体中等大小。减数分裂中期具12对正常的二价体,但后期I和后期Ⅱ均有染色体异常现象发生。统计断片、落后染色体和染色体桥出现的比例与花粉粒败育性比例比较一致,表明秤锤树的小孢子在发生和发育过程中较高频率的败育现象可能存存一常的细胞学原因．     

FISH分析栽培高梁×拟高梁、甜高梁×拟高梁的染色体行为

采用荧光原位杂交技术对45SrDNA在栽培高梁×拟高粱、甜高梁×拟高梁F,的有丝分裂和减数分裂染色体进行定位研究。在有丝分裂中期染色体上2个杂种分别检测到2个杂交信号,在减数分裂粗线期、终变期、中期Ⅰ染色体上45SrDNA位于一个二价体上,说明这两个杂种携带45SrDNA的染色体为同源染色体。根据45SrDNA位点随细胞减数分裂过程的位置变化,表明这两个杂种染色体配对行为正常,平均构型为2n=2x=20（10Ⅱ）,证明45SrDNA可作为染色体的一个识别指标间接地观察细胞减数分裂过程染色体的变化行为。     

异源六倍体水稻AACCDD和三倍体水稻ACD生殖特性的细胞胚胎学研究

利用异源多倍体杂种优势是多倍体水稻研究的第三阶段,但异源多倍体杂种常常不育。为明确其不育特点,本文以本实验室通过远缘杂交获得的栽培稻（AA）品种DTS137和高秆野生稻O．alta（CCDD）的杂种三倍体ACD和加倍形成的六倍体AACCDD为材料,分别对其花粉和胚囊发育过程进行石蜡切片观察,发现3x与6x之间以及6x雌性和雄性生殖方式和前途具有明显的不同：（1）异源三倍体ACD水稻杂种花粉败育彻底,败育发生在小孢子母细胞时期,绒毡层细胞提前解体：大孢子母细胞不能进行减数分裂,与周围的珠心组织一起发生解体,雌性完全败育。（2）异源六倍体水稻杂种（AACCDD）的雄性败育发生在小孢子母细胞减数分裂的细线期,此期小孢子母细胞发育停滞,随后解体;而雌性器官的发育基本正常。推测异源六倍体杂种的不育性与不同基因组间存在着部分核质不亲和性有关。据此,为了克服六倍体水稻AACCDD的不育性和验证该杂种雌性可育的结论,以栽培稻（AA）的PMeS二倍体品系HN2026．2x为父本与之杂交,通过胚挽救成功获得回交杂种BC1F1植株,经根尖染色体鉴定为2n=4x=48,系由AACD组成。虽然该异源三基四倍体是不育的,但为随后的染色体加倍创造AAAACCDD同源异源八倍体,进而获得结实的同源异源多倍体杂种打下了良好的基础。     

细胞学方法在木兰科杂交育种早期鉴定中的应用

研究了木兰科 1个属内种间杂交组合红花山玉兰 (Magnoliadelavayi) (♀ )×广玉兰(M grandiflora) (♂ )和 1个属间杂交组合红花山玉兰 (♀ )×乐东拟单性木兰 (Parakmerialotungensis) (♂ )的亲本及F1代的染色体数目和形态。结果表明 ,前者的杂交后代染色体数目为 76条 ,正好是二倍体红花山玉兰 (2n =2x =38)和六倍体广玉兰 (2n =6x =114 )的半数之和 ,且在F1代的分裂中期染色体具大小两种类型 ,可以明显看出来自红花山玉兰的染色体较大 ,而来自广玉兰的染色体较短小 ,这证明该F1为两者的杂交种 ;而后者的杂交后代染色体数仅为 38条 ,而不是二倍体山玉兰和六倍体乐东拟单性木兰 (2n =6x =114 )的半数之和 ,且所有染色体形态都与红花山玉兰相同这证明该F1代不是真正的杂交种 ,可能是无融合生殖的结果。本研究结果表明细胞学方法是木兰科植物杂交育种中早期检测的有效方法之一。     

云南山茶花四倍体的首次发现及其科学意义

本文对分布于云南和四川金沙江河谷的云南山茶花C. reticulata及其两个近缘种(怒江山茶C.saluenensis和西南山茶C．pitardii)进行了细胞学研究。34个居群的云南山茶花中,21个居群是四倍体类型(2n=60),11个居群是六倍体类型(2n=90),另2个居群为二倍体(2n=30),云南山茶花的四倍体类型为首次发现,并且进行了核形态研究。四倍体和六倍体的花粉母细胞减数分裂染色体构型在大多数居群都为二价体(四倍体中30个二价体,六倍体中45个二价体),少数居群或是个体除二价体为主外还出现单价体和四价体,六倍体类型没有出现六价体构型。根据减数分裂的构型,我们认为,四倍体和六倍体分别为异源四倍体和异源六倍体,少数四价体的存在表明染色体有部分同源性。所有四倍体和六倍体的体细胞间期核特征和前期染色体形态特征基本相似。中海拔(1800m)以上的四倍体的云南山茶花外部形态特征与六倍体类型比较相似,而低海拔(1100～1800 m)的四倍体类型的外部形态特征则有些不同,但核形态结构是比较相似的。四倍体与六倍体类型地理分布是连续的,并与近缘的二倍体种怒江山茶、西南山茶重叠分布。     

普通小麦Ph基因缺失的遗传效应

普通小麦(2n=6x=42)由A、B、D 3个染色体组构成。据研究,这3组染色体之间存在着部分同源关系。但在正常情况下,具有部分同源关系的染色体在减数分裂时并不发生配对,而只限于同源染色体之间进行配对。于是,在减数分裂中期Ⅰ看到的是21个二价体。1957     

埃塞俄比亚芥与芥蓝杂交获得异源三倍体及其细胞学研究

以埃塞俄比亚芥(2n=4x=BBCC=34)和芥蓝(2n=2x=CC=18)为材料,通过相互杂交获得了异源三倍体(2n=3x=BCC=26)。该异源三倍体生长势较强;叶色等介于双亲之间;株型、花型和花大小偏向于埃塞俄比亚芥;花色与芥蓝的相同,为白花。减数分裂观察表明:在终变期,一般形成9个二价体和8个单价体(9Ⅱ+8Ⅰ),且B、C两组染色体表现出一定程度的分群现象;中期Ⅰ,CC基因组的9个二价体排列在赤道板上,而B组的8个单价体游离在赤道板周围;后期Ⅰ分到两极的染色体以13/13和12/14占多数,偶见落后的染色体。该BCC异源三倍体的获得为创建CC+B染色体的异附加系和研究B、C基因组间的亲缘关系奠定了基础。     

番木瓜核型和减数分裂研究

对番木瓜核型和花粉母细胞减数分裂行为的研究表明,番木瓜染色体数目为2n=18,由9对中部着丝粒染色体组成。核型公式为2n=2x=18m。花粉母细胞减数分裂正常,在终变期和中期Ⅰ观察到9个二价体,未观察到染色体结构变异和行为异常。     

黄芩的花粉母细胞减数分裂及核型分析

采用压片法,对黄芩花粉母细胞减数分裂及核型进行了研究。结果表明:黄芩的大多数花粉母细胞减数分裂中染色体的行为正常,在终变期同源染色体配对后可形成9个二价体,后期Ⅰ染色体以9∶9的方式向细胞两极分离,其减数分裂为同时型;在少数花粉母细胞减数分裂中观察到落后染色体、染色体桥等异常行为;其花粉粒育性为76.49%。黄芩的染色体数目为2n=2X=18,核型公式为K(2n)=2X=18=16m+2 sm,染色体相对长度组成为2n=1 s+4M1+3M2+1L,其核型为"1A"型。     

Chromosome numbers, meiotic behavior, and pollen viability of species of Vriesea and Aechmea genera (Bromeliaceae) native to Rio Grande do Sul, Brazil

Chromosome number, meiotic behavior, and pollen viability were analyzed in 15 species of two genera, Vriesea and Aechmea, native to Rio Grande do Sul, Brazil. This study is the first cytogenetic analysis of these taxa. The chromosome numbers are all n = 25, consistent with the proposed base number of x = 25 for Bromeliaceae. All examined taxa displayed regular bivalent pairing and chromosome segregation at meiosis. Observed meiotic abnormalities include univalents in metaphase I; missing or extra chromosomes and precocious division of centromeres in metaphase II; laggards in telophase I and anaphase II/telophase II. The high pollen viability (>88%) reflects a regular meiosis.     

Inverted meiosis and its place in the evolution of sexual reproduction pathways

Inverted meiosis is observed in plants (Cyperaceae and Juncaceae) and insects (Coccoidea, Aphididae) with holocentric chromosomes, the centromeres of which occupy from 70 to 90% of the metaphase chromosome length. In the first meiotic division (meiosis I), chiasmata are formed and rodlike bivalents orient equationally, and in anaphase I, sister chromatids segregate to the poles; the diploid chromosome number is maintained. Non-sister chromatids of homologous chromosomes remain in contact during interkinesis and prophase II and segregate in anaphase II, forming haploid chromosome sets. The segregation of sister chromatids in meiosis I was demonstrated by example of three plant species that were heterozygous for chromosomal rearrangements. In these species, sister chromatids, marked with rearrangement, segregated in anaphase I. Using fluorescent antibodies, it was demonstrated that meiotic recombination enzymes Spo11 and Rad5l, typical of canonical meiosis, functioned at the meiotic prophase I of pollen mother cells of Luzula elegance and Rhynchospora pubera. Moreover, antibodies to synaptonemal complexes proteins ASY1 and ZYP1 were visualized as filamentous structures, pointing to probable formation of synaptonemal complexes. In L. elegance, chiasmata are formed by means of chromatin threads containing satellite DNA. According to the hypothesis of the author of this review, equational division of sister chromatids at meiosis I in the organisms with inverted meiosis can be explained by the absence of specific meiotic proteins (shugoshins). These proteins are able to protect cohesins of holocentric centromeres from hydrolysis by separases at meiosis I, as occurs in the organisms with monocentric chromosomes and canonical meiosis. The basic type of inverted meiosis was described in Coccoidea and Aphididae males. In their females, the variants of parthenogenesis were also observed. Until now, the methods of molecular cytogenetics were not applied for the analysis of inverted meiosis in Coccoidea and Aphididae. Evolutionary, inverted meiosis is thought to have appeared secondarily as an adaptation of the molecular mechanisms of canonical meiosis to chromosome holocentrism.     

鸭跖草科杜若(Pollia japonica Thunb.)的减数分裂研究

首次对鸭跖草科杜若(Pollia japonicaThunb.)进行了花粉母细胞减数分裂观察,并重新报道了该种的染色体数目为2n=32。结果显示,减数分裂中期I构型为16Ⅱ,并且观察到次级联会现象。减数分裂后期I和后期Ⅱ存在落后染色体、染色体断片、二次分裂不同步等异常现象,统计各时期畸形率都低于10%。随机统计花粉粒活性,成熟率达到90%以上。这说明杜若的减数分裂过程基本正常,也证明了2n=32的体细胞染色体数目是可信的。     

TRANSMISSION AND SIGNIFICANCE OF B CHROMOSOMES IN ANTHURIUM WAROCQUEANUM

Somatic and meiotic chromosomes of one plant of Anthurium warocqueanum J. Moore and its selfed offspring were analyzed. The parent showed 2n = 30 + 3B in both somatic cells and pollen mother cells. The B chromosomes divided normally in somatic cells, but meiotic associations of Bs varied. Three configurations of three B chromosomes were observed at metaphase I of parent meiosis: one trivalent, one bivalent and one univalent, or three univalents. The number of B chromosomes in offspring ranged from 0 to 6, indicating their transmission from both male and female gametes. Offspring with two B chromosomes appeared in greatest frequency. It was hypothesized that both male and female gametes of the 3 B parent frequently contained one B chromosome through the normal distribution of the bivalent Bs at meiosis and the elimination of the univalent B chromosome due to lagging. Examination of pollen mother cells of offspring also revealed irregular behavior of B chromosomes. With a high number of B chromosomes, normal A chromosome bivalent formation seemed to be reduced. No phenotypic effects of B chromosomes were observed.     

濒危植物巴东木莲花粉母细胞减数分裂观察

对巴东木莲Manglietia patungensis及其近缘种乳源木莲M. yuyuanensis的花粉母细胞减数分裂过程的基本特征进行了比较研究。乳源木莲与巴东木莲的染色体数目和核型相同,但不经任何人为因素诱导,它们之间在减数分裂过程中的染色体行为上有明显差异。(1)巴东木莲减数分裂中期I构型为0.30IV+18.33II+0.15I,与乳源木莲构型19II不同,巴东木莲可能存在同臂内倒位杂合子,染色体结构存在一定的杂合性。(2)后期I和后期II染色体行为异常现象发生频率明显不同。以后期II为例,乳源木莲减数分裂相中有迟滞染色体的细胞占8.8%,迟滞染色体不超过2个;巴东木莲有迟滞染色体等异常现象的细胞占29.2%,迟滞染色体最高达11个,还出现染色体碎裂成断片现象。巴东木莲减数分裂过程中染色体组表现出染色体结构杂合变异和迟滞染色体与染色体的断裂频率很高的异常现象在一定程度上可能影响了雄配子体的发育。     

Chromosome pairing and potential for intergeneric recombination in some hypotetraploid somatic hybrids of Lycopersicon esculentum (+) Solanum tuberosum.

Three somatic hybrids resulting from protoplast fusions of a diploid kanamycin-resistant line of tomato (Lycopersicon esculentum) and a dihaploid hygromycin-resistant transformant of a monohaploid potato (Solanum tuberosum) line were used for a cytogenetic study on chromosome pairing and meiotic recombination. Chromosome counts in root-tip meristem cells revealed two hypotetraploids with chromosome complements of 2n = 46 and one with 2n = 47. Electron microscope analyses of synaptonemal complex spreads of hypotonically burst protoplasts at mid prophase I showed abundant exchanges of pairing partners in multivalents involving as many as eight chromosomes. In the cells at late pachytene recombination nodules were found in multivalents on both sides of pairing partner exchanges, indicating recombination at both homologous and homoeologous sites. Light microscope observations of pollen mother cells at late diakinesis and metaphase I also revealed multivalents, though their occurrence in low frequencies betrays the reduction of multivalent number and complexity. Precocious separation of half bivalents at metaphase I and lagging of univalents at anaphase I were observed frequently. Bridges, which may result from an apparent inversion loop found in the synaptonemal complexes of a mid prophase I nucleus, were also quite common at anaphase I, though the expected accompanying fragments could be detected in only a few cells. Most striking were the high frequencies of first division restitution in preparations at metaphase II/anaphase II, giving rise to unreduced gametes. In spite of the expected high numbers of balanced haploid and diploid gametes, male fertility, as revealed by pollen staining, was found to be negligible.     

Lack of Checkpoint Control at the Metaphase/Anaphase Transition: A Mechanism of Meiotic Nondisjunction in Mammalian Females

A checkpoint mechanism operates at the metaphase/anaphase transition to ensure that a bipolar spindle is formed and that all the chromosomes are aligned at the spindle equator before anaphase is initiated. Since mistakes in the segregation of chromosomes during meiosis have particularly disastrous consequences, it seems likely that the meiotic cell division would be characterized by a stringent metaphase/ anaphase checkpoint. To determine if the presence of an unaligned chromosome activates the checkpoint and delays anaphase onset during mammalian female meiosis, we investigated meiotic cell cycle progression in murine oocytes from XO females and control siblings. Despite the fact that the X chromosome failed to align at metaphase in a significant proportion of cells, we were unable to detect a delay in anaphase onset. Based on studies of cell cycle kinetics, the behavior and segregation of the X chromosome, and the aberrant behavior and segregation of autosomal chromosomes in oocytes from XO females, we conclude that mammalian female meiosis lacks chromosome-mediated checkpoint control. The lack of this control mechanism provides a biological explanation for the high incidence of meiotic nondisjunction in the human female. Furthermore, since available evidence suggests that a stringent checkpoint mechanism operates during male meiosis, the lack of a comparable checkpoint in females provides a reason for the difference in the error rate between oogenesis and spermatogenesis.     

Chromosomal interchange inEleutherine plicata Herb

Chromosome behaviour at metaphase I and anaphase I of meiosis inEleutherine plicata Herb. (2n=14) is studied. Cells with chromosome associations comprising an association of four long chromosomes, in addition to five bivalents were observed more frequently than those with seven bivalents. it is concluded that the ring of four is due to a segmental interchange between the two long non-homologous chromosome pairs. The ring of four at anaphase I showed delayed disjunction, bridge formation and irregular separation of chromosomes in a number of cells while the behaviour of the other bivalents was normal.