四价染色体

At diakinesis, 0.2 tetravalents, 0.05 hexavalents and 0.05 octovalents per pollen mother cell were detected, which was absent in cultivated cucumber. In 30% PMCs, crossed chromosomes occurred at diakinesis.

在减数分裂终变期，平均每个花粉母细胞有0.2个四价体、0.05个六价体和0.05个八价体，约30%的花粉母细胞中存在拉十字的染色体。

Barley seeds were irradiated with five different doses of 60 Co-γ ray.There were many kinds of chromosome aberration in pollen mother cells,such as bridge,laggards in anaphase I and anaphase II,asymmetrical division in anaphase I and asynchronous division in anaphase II,ring quadrivalent in metaphase I,three pole division and micro-nuclei in telophase I,micro-nuclei in tetrad and some micro-nucleus separates from the tetrad to form polyad.

大麦种子经5种不同剂量γ射线辐照后， M1植株的花粉母细胞出现多种染色体畸变类型，例如后Ⅰ、后Ⅱ中出现桥、落后，后Ⅰ中出现不对称分裂，后Ⅱ中出现不同步分裂，中期Ⅰ出现环状四价体，末期Ⅰ中有三极分裂和微核，四分体中出现微核且有的微核独立于四分体，从而形成多分体。

Results showed that the PMC meiosis of autotetraploid was similar to the diploid except some particularities. In metaphase Ⅰ, multivalent, quadrivalent, trivalent, bivalent and univalent were observed and some of the chromosomes were found not to rank on the metaphase plate and so did in metaphase Ⅱ cells. In anaphase Ⅰ and anaphase Ⅱ cells, there were lagging chromosomes, chromosome bridge and fragment. During anaphase Ⅱ and telophase Ⅱ, chromosome segregation was not synchronous or equal. At tetrad stage, dyad, triad, tetrad with micronucleus and polyad appeared.

结果表明，同源四倍体花粉母细胞减数分裂过程与二倍体相比，中期Ⅰ染色体构型复杂，有多价体、四价体、三价体、二价体和单价体；中期Ⅰ及中期Ⅱ有部分染色体没有排列在赤道板上；后期Ⅰ及后期Ⅱ出现落后染色体、染色体桥及断片；后期Ⅱ和末期Ⅱ有染色体不同步分离及不等分裂的现象；四分体时期还出现二分体、三分体、含微核的异常四分体及多分体。

The result showed that the plant of Maicao No. 9 was tall, with good fecundity, fully filled grain and vigorous growth. The chromosome number of the root cells was 2n=56, through the observation of pollen mother cells meiosis, there were a certain amount of univalents, ring bivalents and bar bivalents in PMCM. Different numbers of lagging chromosomes, chromosome bridges and micronucleus were found in anaphaseⅠ, anaphaseⅡ and tetraspore.

结果表明：麦草9号植株高大，结实性较好，籽粒饱满，生长旺盛；根尖细胞染色体数目为2n=56，对其进行花粉母细胞减数分裂观察，中期Ⅰ具有一定数量的单价体、环状二价体、棒状二价体；后期Ⅰ、后期Ⅱ与四分体时期都出现不同数量的落后染色体、染色体桥、微核等现象。

The cytogenetics of interspecific hybrids among the four cultivated cotton species were studied in this paper and results are as follows: The diploid interspecific hybrid (G. arboreum×G. herbacium) F〓 had a four-chromosome-ring at the meiotic metakinesis. The synapses of tetraploid hybrid (G. hirsutum ×G. barbadense) F〓 was found to be regular, which mainly formed bivalents, sometimes some univalents, multivalents and chromosome bridge.

四个栽培棉种间杂交种F〓的细胞学观察结果表明，F〓减数分裂中期Ⅰ，形成一个环状四价体，直接证明了亚洲棉与草棉之间存在一对相互易位；F〓减数分裂中期Ⅰ联会基本正常，主要形成二价体，偶尔出现一些单价体和多价体，以及染色体桥。

The results showed that: at metaphase I, the homoeologous chromosome pairing among different F1 hybrids ranged from 2.0 to 11.4 bi-valents formed by homoeologous chromosomes per pollen mother cell, and very few multivalents, and even very few bivalents were formed by two chromosomes within one genome rather than homoeologous chromosomes in some PMCs; at anaphase I, all biva-lents were disjoined and most univalents were divided.

结果表明在中期I阶段，这些杂种一代的近缘染色体联会变化很大，每个花粉母细胞中二价体形成的数目从平均2个到11.4个不等，甚至在某些花粉母细胞中，还发现极少的多价体和非部分同源染色体所形成的单基因组内二价体；在后期I时，所有的二价体分离，同时多数单价体也分离，分离的二价体和分离的单价体都移向两极，从而形成两组染色体；因为这时完整花粉母细胞中分离的二价体在两组染色体中总是对应出现，从而根据半二价体上染色体重组的位置可以分析在二价体的四分体时期发生在非姊妹染色体之间的多种染色体交换类型，如单交换、三线双交换、四线双交换、四线三交换和四线多交换。

Thus, the meiotic chromosome cofigurations showed that the tetraploids and hexaploids in C.reticulata allopolyploids, and the appearance of a few tetravalents in some populations might indicatehomology of chromosomes in different genomes to some extent.

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。

In meiosis of pollen mother cells of the tetraploids and the hexaploids, only bivalents were observed in most of the populations, although in several populations or individuals a few univalents or tetravalents appeared. In the hexaploids, hexavalents were not observed.

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。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了