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嫁接,能形成无性杂种吗
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作者 张德华 《天水师范学院学报》 1986年第2期72-75,79,共5页
众所周知,生物变异是生物进化的基础,没有变异,就没有进化。而导致变异出现的一个重要途径是遗传物质的重组。 在植物界中,遗传重组主要是通过有性生殖来实现的。但在一些低等物物,如细菌、真菌和某些藻类中,“无性重组”也占有相当重... 众所周知,生物变异是生物进化的基础,没有变异,就没有进化。而导致变异出现的一个重要途径是遗传物质的重组。 在植物界中,遗传重组主要是通过有性生殖来实现的。但在一些低等物物,如细菌、真菌和某些藻类中,“无性重组”也占有相当重要的地位,这种无性重组可以通过转化、转导、接合等无性过程来实现[1]。 展开更多
关键词 无性杂种 生物变异 遗传重组 植物界 生物进化 异源染色体 嫁接技术 愈合组织 中间性状 染色体配对
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显微镜下描述痣和黑色素瘤的色素网状结构和细胞构造
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作者 Pellacani G. Cesinaro A.M. +1 位作者 Longo C. 阎小宁 《世界核心医学期刊文摘(皮肤病学分册)》 2005年第6期48-49,共2页
Objective: To characterize the microscopic aspects of the dermoscopic pigment network in vivo, by means of confocal scanning laser microscopy. Design: Confocal imaging was performed on melanocytic lesions characterize... Objective: To characterize the microscopic aspects of the dermoscopic pigment network in vivo, by means of confocal scanning laser microscopy. Design: Confocal imaging was performed on melanocytic lesions characterized by pigment network at dermoscopy. Some confocal architectural and cytologic features, as observed at the dermoepidermal junction, were morphologically described and quantified by means of a dedicated program. Setting: University medical department. Study Population: We studied confocal images of 15 melanomas, 15 dermoscopic atypical nevi, and 15 common nevi. Main Outcome Measures: Features referring to aspect, size, regularity, homogeneity, and infiltration of dermal papillae and to cellular size, regularity, and atypia were described by 2 observers on confocal images. Mean dermal papillary diameter, mean cell area, and shape irregularity were quantified by drawing papillae and cell contours on confocal images and measured with the use of a computer program. Results: Pigment network in melanomas consisted of large basal cells that circumscribed small to medium-sized dermal papillae with marked cellular atypia, sometimes infiltrating dermal papillae. On the other hand, common acquired nevi were characterized by lack of atypical cells and edged dermal papillae. Atypical nevi presented intermediate characteristics between clearly benign and malignant lesions. Conclusion: Cellular atypia was the most sensitive feature for melanoma diagnosis, whereas the presence of nucleated cells infiltrating dermal papillae was the most specific one. 展开更多
关键词 黑色素瘤 真皮乳头 黑素瘤 活体内 非典型性 显微结构 中间性状 同质性
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