共查询到20条相似文献,搜索用时 62 毫秒
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用风油精预处理制备植物染色体标本的新方法 总被引:3,自引:0,他引:3
目前,在植物细胞染色体的研究工作中,常用的染色体预处理药物为秋水仙素、对二氯苯、α-溴萘和8-羟基喹啉等。我们经过多次对水稻、绿豆等小型染色体植物的摸索,发现风油精也可作为一种新的植物染色体预处理药物。水稻、绿豆的根尖经风油精预处理后,可以省去常规的酸解压片和酶解去壁低渗步骤而直接捣碎涂片,制得的标本可获得良好的染色体图象。我们将这一方法称为风油精法。何凤发等将此法加以改进应用于高梁、芝麻和荞麦等小型染色体植物中也得到了满意的结果。因而,风油精法比较适合于小型染色体植物的染色体标本制备。本文介绍这一新方法。 相似文献
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人类细胞减数分裂是精卵形成过程中的重要阶段。它包括染色体的一次复制 ,细胞的两次连续的分裂以及同源染色体配对、交换 ,同源染色体分离 ,姐妹染色单体分离等一系列复杂的过程。在细胞分裂进入中、后期时 ,如果其一对同源染色体或两姐妹染色单体未分别向两极移动 ,却同时进入一个子细胞中 ,结果细胞分裂所形成的两个子细胞中 ,一个将因染色体数目增多而形成超二倍体 ,一个则由于染色体数目减少而形成亚二倍体。这一过程称染色体不分离 (chromosomalnon -disjunction) ,从而引起配子中染色体数目异常 ,产生非整… 相似文献
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濒危植物矮沙冬青减数分裂期染色体行为的观察 总被引:8,自引:1,他引:8
用涂片法和酶解法,观察了濒危植物矮沙冬青的减数分裂过程。在减数分裂双线期末或终变期初,可以观察到9个二价体,在中期Ⅰ末至后期Ⅰ初,同源染色体基本排列在赤道板上,然后在纺锤丝的牵引下二价体的两条同源染色体分开,分别移向两极,每一极有9条染色体,从而确认该属植物的染色体基数为x=9。在矮沙冬青减数分裂过程中,没有发现染色体有异常行为,认为其小孢子形成过程正常。因此认为矮沙冬青濒危不是染色体行为异常和小孢子发育不正常而造成的。 相似文献
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过塑制作和保存植物蜡叶标本 总被引:1,自引:0,他引:1
多年来,我们一直组织学生采集和制作植物蜡叶标本,并从中选取一些做为直观教具,以加强课堂直观教学,调动学生的积极性。在实践过程中,我们从照相馆利用过塑机给相片过塑能很好地保存照片这一点受到启发,利用过塑机给植物蜡叶标本过塑,效果很好。这类型标本不仅形态清晰、平展、美观大方,而且牢固,密封性好,易于保存,在教学中运用,受到学生们的欢迎。现介绍具体做法如下: 1、根据教学内容和要求,将采集来的各类植物标本给予整理、压制、干燥。 2、把干燥处理后的标本,用万能胶将标本固定在台纸上,安放标本时要注意科学 相似文献
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利用整体压片法 ,对分别隶属于球角科和长角科的两种跳虫似微小球角 (Hypogastruraadex ilis (Stach ,196 4 ) )和曲毛裸长 (SinellacurvisetaBrook 1889)的染色体进行了首次观察。发现似微小球角单倍染色体数目n =7,雄性有 13条染色体 ,雌性有 14条 ,为XO型性别决定 ;曲毛裸长n =6 ,雄性 2n =11,雌性 2n =12 ,同样为XO型性别决定。还记述了雄性似微小球角的减数分裂过程 :在分裂前期 ,同源染色体进行配对 ;部分同源染色体发生交叉 ,部分仅末端相连 ;早后期Ⅰ ,当常染色体向两极移动时 ,性染色体仍滞后于赤道板中央。 相似文献
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利用荧光原位杂交技术分析了两个小麦-外源种杂种花粉母细胞中1BL/1RS 小麦-黑麦易位染色体和外源染色体包括中间偃麦草(Thinopyrum intermedium (Host) Barkworth & DR Dewey)、簇毛麦(Haynaldia villosa (L.) Schur)染色体的减数分裂行为. 我们首次发现:在减数分裂后期, 1BL/1RS 小麦-黑麦易位染色体发生错分裂,形成两个易位染色单体. 这种错分裂导致易位染色单体在末期Ⅰ分配到两个正在形成的细胞核内,错分裂的易位染色单体进一步形成微核,并在四分体期观察到黑麦的微核出现.从贵农22×遗4095 的F2代植株中检测到一个2n=41的植株,其含有一对1BL/1RS 小麦-黑麦易位染色体,核型分析表明,其中一条黑麦染色体臂比另一条的黑麦染色体臂短1/3左右.在遗4212×遗4095的F2代中检测到一个具有中间偃麦草染色体小片段易位到小麦染色体端粒部分的小麦-中间偃麦草易位植株.这可能是由于在减数分裂过程中发生非均等分裂导致小麦-黑麦1BL/1RS易位染色体的黑麦染色体段臂缺失1/3及小麦-中间偃麦草非罗伯逊易位.在两个杂种F2植株中,中间偃麦草染色体分布频率为39.6%, 簇毛麦染色体分布频率为43.4%, 1BL/1RS 小麦-黑麦易位染色体分布频率分别为51.8%和56.6%.实验结果表明,1BL/1RS 小麦-黑麦易位染色体与外源染色体包括中间偃麦草、簇毛麦染色体在减数分裂过程中没有相互作用.小麦-黑麦1BL/1RS易位染色体在减数分裂过程中可以发生错分裂,并导致杂种后代黑麦染色体臂发生缺失.这对于培育以小麦为背景含有不同长度的黑麦1R染色体短臂的种质及小麦-外源染色体非罗伯逊易位的小片段易位系具有指导意义. 相似文献
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Heyting C 《Transgenic research》2005,14(5):547-550
Meiosis is a specialized set of two nuclear divisions, meiosis I and II, by which a diploid cell produces four haploid daughters.
After premeiotic DNA replication, homologous chromosomes pair and recombine, and then disjoin at meiosis I. Subsequently,
at meiosis II, the sister chromatids of each chromosome segregate. In nearly all eukaryotes, meiotic chromosome pairing culminates
in the formation of a ladderlike supramolecular protein structure, the synaptonemal complex (SC) (Page and Hawley, 2004).
The rungs of the ladder are known as transverse filaments (TFs). Genes encoding TF proteins have been identified in a limited
number of organisms, and their function has been studied by mutational analysis. Although TF proteins show little amino acid
sequence conservation, their structure and function are largely conserved. In all analyzed species, TF proteins are required
for meiotic reciprocal recombination (crossing over). 相似文献
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Paula M. Checchi Katherine S. Lawrence Mike V. Van Braden J. Larson JoAnne Engebrecht 《Genetics》2014,197(2):543-560
During meiosis, accurate chromosome segregation relies on homology to mediate chromosome pairing, synapsis, and crossover recombination. Crossovers are dependent upon formation and repair of double-strand breaks (DSBs) by homologous recombination (HR). In males of many species, sex chromosomes are largely hemizygous, yet DSBs are induced along nonhomologous regions. Here we analyzed the genetic requirements for meiotic DSB repair on the completely hemizygous X chromosome of Caenorhabditis elegans males. Our data reveal that the kinetics of DSB formation, chromosome pairing, and synapsis are tightly linked in the male germ line. Moreover, DSB induction on the X is concomitant with a brief period of pseudosynapsis that may allow X sister chromatids to masquerade as homologs. Consistent with this, neither meiotic kleisins nor the SMC-5/6 complex are essential for DSB repair on the X. Furthermore, early processing of X DSBs is dependent on the CtIP/Sae2 homolog COM-1, suggesting that as with paired chromosomes, HR is the preferred pathway. In contrast, the X chromosome is refractory to feedback mechanisms that ensure crossover formation on autosomes. Surprisingly, neither RAD-54 nor BRC-2 are essential for DSB repair on the X, suggesting that unlike autosomes, the X is competent for repair in the absence of HR. When both RAD-54 and the structure-specific nuclease XPF-1 are abrogated, X DSBs persist, suggesting that single-strand annealing is engaged in the absence of HR. Our findings indicate that alteration in sister chromatid interactions and flexibility in DSB repair pathway choice accommodate hemizygosity on sex chromosomes. 相似文献
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As a part of our program to explore and evaluate genetic diversity of flowering plants of the Kashmir Himalayas,meiotic studies have been carried out on 150 wild species.Of these,Caltha alba (2n =32),D... 相似文献
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Increasing age in a woman is a well-documented risk factor for meiotic errors, but the effect of paternal age is less clear. Although it is generally agreed that spermatogenesis declines with age, the mechanisms that account for this remain unclear. Because meiosis involves a complex and tightly regulated series of processes that include DNA replication, DNA repair, and cell cycle regulation, we postulated that the effects of age might be evident as an increase in the frequency of meiotic errors. Accordingly, we analyzed spermatogenesis in male mice of different ages, examining meiotic chromosome dynamics in spermatocytes at prophase, at metaphase I, and at metaphase II. Our analyses demonstrate that recombination levels are reduced in the first wave of spermatogenesis in juvenile mice but increase in older males. We also observed age-dependent increases in XY chromosome pairing failure at pachytene and in the frequency of prematurely separated autosomal homologs at metaphase I. However, we found no evidence of an age-related increase in aneuploidy at metaphase II, indicating that cells harboring meiotic errors are eliminated by cycle checkpoint mechanisms, regardless of paternal age. Taken together, our data suggest that advancing paternal age affects pairing, synapsis, and recombination between homologous chromosomes—and likely results in reduced sperm counts due to germ cell loss—but is not an important contributor to aneuploidy. 相似文献