双染色体分离的

In diplotene the pairs of chromatids begin to separate from the tetrad formed by the association of homologous chromosomes. Chiasmata can often be seen at this stage.

双线期时，配对的染色单体开始从四分体中分离，此时常可见染色体交叉。

Methods Lymphocytes were obtained from healthy donors of different ages, both sexes, and were treated with cytochalasin B. Binucleated cells were hybridized with chromosome 21 specific probe, and simultaneously, chromosome 21 loss and nondisjunction were detected.

用细胞松弛素B处理不同年龄及性别正常人外周血淋巴细胞获得的双核细胞，以21号染色体近着丝粒特异性探针进行荧光原位杂交，同时检测21号染色体丢失及不分离。

The open reading frame of Spinacia oleracea Betaine Aldehyde Dehydrogenase was retrieved from Spinacia oleracea and inserted into the Agrobacterium tumefaciens binary vector pBin438, which was driven by CaMV35S promoter, and produced the new binary vector pBSB. A. tumefaciens LBA4404 carrying this plasmid was used in genetic transformation of plants. Forty-five primary transgenic plants were detected by PCR and verified by the Southern blotting from 65 regenerated plants, of which 27 transgenic plants had only one copy of T-DNA.

摘 要：分离出菠菜甜菜碱醛脱氢酶基因构建成由CaMV35S驱动的双元植物表达载体pBSB，农杆菌菌株LBA4404携带该载体转化棉花，获得转基因棉花植株。65株转基因植株经过PCR筛选、Southern blotting分析证明有45株为成功的转化株，外源基因已经被整合到棉花的染色体组中，并以单拷贝插入居多。

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。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。