DNA指纹技术从原理上可以分为两大类:即传统的以Southern杂交为基础的RFLP技术和以聚合酶链式反应(PCR)为基础的一系列分子标记技术.RFLP需要样品DNA的量较大,对微量被测样品无能为力.至于与PCR相结合的RAPD、AP-PCR和DAF等技术则由于...DNA指纹技术从原理上可以分为两大类:即传统的以Southern杂交为基础的RFLP技术和以聚合酶链式反应(PCR)为基础的一系列分子标记技术.RFLP需要样品DNA的量较大,对微量被测样品无能为力.至于与PCR相结合的RAPD、AP-PCR和DAF等技术则由于引物相对较短,对实验条件非常敏感,每一轮实验都需要筛选最合适的反应体系,增加了实验周期和复杂度.近几年新出现的AFLP(Amplified Fragment Length Polymorphism)、LPRAPD(Long Primer RAPD)和DALP(DirectAmplification of Length Polymorphism)技术弥补了上述不足.展开更多
Using DGD embedment_free electron microscopy, ultrastructural observation on the intra_ and intercellular microtrabecular network (MN) of the pollen mother cells (PMC) of the whole meiotic prophase Ⅰ in onion ( Alli...Using DGD embedment_free electron microscopy, ultrastructural observation on the intra_ and intercellular microtrabecular network (MN) of the pollen mother cells (PMC) of the whole meiotic prophase Ⅰ in onion ( Allium cepa L.) was performed. Complex nuclear MN was observed in the nucleus of PMCs, spreading throughout the nuclear region. The nucleolus and chromosomes were connected with the MN filament network. The uniformity of nuclear MN changed with the development of the PMCs. A lamina_like structure surrounded the nucleus and joined the MN in nucleus and in cytoplasm, but it disassembled at the end of prophase Ⅰ. There was also a complex cytoplasmic MN in PMCs, without obvious variation during the prophase Ⅰ. Furthermore, MN in cytoplasmic connections (plasmodesmata and cytoplasmic channels) was noticed to link the frameworks in two neighboring PMCs into one entity. Cytomixis was observed at synizesis of prophase Ⅰ in this experiment, and MN in cytoplasm and in nucleus was noticed to distribute in these granules which migrated from one PMC into its neighboring cell. At this time the nucleus moved aside from center of the PMC, but the rest of the cell was still fulfilled with MN filaments. The relationships of nuclear MN with nucleolus and chromosomes, lamina with nucleus, as well as intra_ and intercellular MN with cytomixis are discussed in this paper.展开更多
文摘DNA指纹技术从原理上可以分为两大类:即传统的以Southern杂交为基础的RFLP技术和以聚合酶链式反应(PCR)为基础的一系列分子标记技术.RFLP需要样品DNA的量较大,对微量被测样品无能为力.至于与PCR相结合的RAPD、AP-PCR和DAF等技术则由于引物相对较短,对实验条件非常敏感,每一轮实验都需要筛选最合适的反应体系,增加了实验周期和复杂度.近几年新出现的AFLP(Amplified Fragment Length Polymorphism)、LPRAPD(Long Primer RAPD)和DALP(DirectAmplification of Length Polymorphism)技术弥补了上述不足.
文摘Using DGD embedment_free electron microscopy, ultrastructural observation on the intra_ and intercellular microtrabecular network (MN) of the pollen mother cells (PMC) of the whole meiotic prophase Ⅰ in onion ( Allium cepa L.) was performed. Complex nuclear MN was observed in the nucleus of PMCs, spreading throughout the nuclear region. The nucleolus and chromosomes were connected with the MN filament network. The uniformity of nuclear MN changed with the development of the PMCs. A lamina_like structure surrounded the nucleus and joined the MN in nucleus and in cytoplasm, but it disassembled at the end of prophase Ⅰ. There was also a complex cytoplasmic MN in PMCs, without obvious variation during the prophase Ⅰ. Furthermore, MN in cytoplasmic connections (plasmodesmata and cytoplasmic channels) was noticed to link the frameworks in two neighboring PMCs into one entity. Cytomixis was observed at synizesis of prophase Ⅰ in this experiment, and MN in cytoplasm and in nucleus was noticed to distribute in these granules which migrated from one PMC into its neighboring cell. At this time the nucleus moved aside from center of the PMC, but the rest of the cell was still fulfilled with MN filaments. The relationships of nuclear MN with nucleolus and chromosomes, lamina with nucleus, as well as intra_ and intercellular MN with cytomixis are discussed in this paper.
