“生物膜的流动镶嵌模型”基于科学史的教学设计

利用生物膜研究的科学史资料,引导学生进行基于资料的课堂探究性学习,注重学生自主、合作、探究的学习方式,达成知识、能力、情感态度与价值观的三维目标。     

“生物膜的流动镶嵌模型”一节教学设计

在“生物膜的流动镶嵌模型”一节教学中,通过自主建构模型,学生在真实情境中分析关键问题,深度挖掘现象背后的本质规律,运用合理的科学方法解决实际问题。在教学过程中注重培养学生的高阶思维和解决真实情境问题的能力。     

“生物膜的流动镶嵌模型”单元式教学设计

构建6个主题单元：①变形虫告诉我们（导入）；②模型构建中的逻辑推理和实验观察；③实验技术进步对生物膜研究的作用；④模型构建中结构与功能的适应；⑤假说的提出和修正；⑥体验美和创造关（结尾），着力于知识的理解、创新精神和实践能力的培养以及情感的渗透。     

“生物膜的流动镶嵌模型”一节的难点突破

人教版必修1第4章第2节＂生物膜的流动镶嵌模型＂一节,其内容涉及的大多是一些＂探索生物膜结构＂的描述性实验,如果直接将这些实验告诉学生,比较枯燥、抽象,远离学生实际生活,学生缺少直观认识。因此,理解和接受起来有些难度,而且又会走上死记硬背的老路上来,体现不了新课改的理念。为解决这一问题,笔者在教学中采用了利用橡皮泥等建构模型以及和课件相结合的教学手段,取得了很好的教学效果。     

"生物膜的流动镶嵌模型"的教学设计

在"生物膜的流动镶嵌模型"的一节教学中,为学生提供充分有效而有序的资料,师生共同合作构建生物膜模型,设计实验方案、相互评价.感受科学家探索的历程和探索过程的艰辛,培养学生"探究、合作、自主"的学习能力.     

“生物膜的流动镶嵌模型”教学中若干问题的分析与处理

“生物膜的流动镶嵌模型”是非常好的科学史教学素材,但在教学中需要深刻理解和解读“暗－亮－暗”图像的含义,深层次地分析生物膜流动性的成因、蛋白质与磷脂双分子层的关系以及磷脂单分子层与水界面的相互作用,才能使知识教学更科学、思维更严密,更有利于学生科学素养的熏陶和培养。     

基于情境创设策略的“生物膜的流动镶嵌模型”教学设计

真实的情境,能增强学生对自然现象的好奇心和求知欲,培养学生的观察能力,促进学生感悟科学探究的基本方法。在"生物膜的流动镶嵌模型"的教学设计中,创设实验等真实的情境,促进学生在学习过程中提升生物学学科核心素养。     

“生物膜的流动镶嵌模型”的教学设计

以科学实验资料为背景创设问题情境,引导学生自主构建生物膜模型和解释生物膜模型等活动,让学生在活动中理解知识的产生过程,形成科学概念,习得科学方法,培养科学精神。     

“基因在染色体上”基于科学史的教学设计

以科学史发展过程中科学家对基因与染色体关系的探索与研究为主线,以基于类比推理、演绎推理、模型构建的科学思维和方法的训练为核心,兼顾科学态度的培养,实现知识、能力、情感态度与价值观的三维教学目标。     

“生物膜的流动镶嵌模型”课堂教学主线设计浅析

笔者研读了新课改以来,同仁对“生物膜的流动镶嵌模型”一节的课堂教学研究成果,对不同的构思均颇有感触,从中提炼出了本节的3种教学主线：三维一体线、模型制作线、逆向思维线。3种教学主线的设计方法,都是属于新课改中热议的模型建构方法。其中前2种主线是顺势思维的模型建构,而第3种则是具有创意的逆向思维的模型建构,它们以不同的方式呈现和诠释着同一主题。3种设计各有优点,在教学过程中,教师可以根据教学实际情况．采用不同的教学主线,甚至可以将不同主线组合起来用。     

A model for estimating the extent of variegation in mosaic tissues

A method is described which allows the size of patches of like cells in mosaic tissues to be estimated from the frequency with which small samples taken from the tissue contain both of the mosaic cell types. The mosaic patches are represented as close-packed geometric figures arranged in twoor three-dimensional tissues. Small samples drawn at random from these tissues will include portions of one or more patches; only those samples which include portions of two or more dissimilar patches (mixed samples) will contain both cell types. The expected frequency of mixed samples is calculated as a function of the shape of the mosaic patches, the frequency of the two mosaic cell types and the sample to patch size ratio. This expected frequency is not strongly dependent on patch shape for triangular, square and hexagonal patches in two dimensions or for cubic and orthotetrakaidekahedral patches in three dimensions. Elongation of square patches along one axis or of cubic patches along one or two axes results in slight increases in the expected frequency of mixed samples for given sample to patch size ratio.     

Evaluation of the conformational switch model for alfalfa mosaic virus RNA replication

Key elements of the conformational switch model describing regulation of alfalfa mosaic virus (AMV) replication (R. C. Olsthoorn, S. Mertens, F. T. Brederode, and J. F. Bol, EMBO J. 18:4856-4864, 1999) have been tested using biochemical assays and functional studies in nontransgenic protoplasts. Although comparative sequence analysis suggests that the 3' untranslated regions of AMV and ilarvirus RNAs have the potential to fold into pseudoknots, we were unable to confirm that a proposed pseudoknot forms or has a functional role in regulating coat protein-RNA binding or viral RNA replication. Published work has suggested that the pseudoknot is part of a tRNA-like structure (TLS); however, we argue that the canonical sequence and functional features that define the TLS are absent. We suggest here that the absence of the TLS correlates directly with the distinctive requirement for coat protein to activate replication in these viruses. Experimental data are evidence that elevated magnesium concentrations proposed to stabilize the pseudoknot structure do not block coat protein binding. Additionally, covarying nucleotide changes proposed to reestablish pseudoknot pairings do not rescue replication. Furthermore, as described in the accompanying paper (L. M. Guogas, S. M. Laforest, and L. Gehrke, J. Virol. 79:5752-5761, 2005), coat protein is not, by definition, inhibitory to minus-strand RNA synthesis. Rather, the activation of viral RNA replication by coat protein is shown to be concentration dependent. We describe the 3' organization model as an alternate model of AMV replication that offers an improved fit to the available data.     

The history of science and the introduction of plant genetics in Mexico

The emergence and development of 'national sciences' in Latin American countries were not, until very recently, part of the agenda of historians of science because the 'traditional' history of sciences was not interested in the scientific activity of peripheral areas. The history of science is a recent discipline in Mexican historiographic studies. The methodological interest in the history of science, the creation of schools and institutes that deal with it, the establishment of particular chairs, the organization of national societies, and the publication of books and periodicals are all very recent. It is important to carry out studies in the history of science that examine the development of Mexican science introducing the 'local' context, and study how this development has influenced the formation of scientific societies and the development of scientific disciplines in the country. We want to explore the introduction of genetics in Mexico as applied to agriculture between 1930 and 1960. This matter has not been investigated in Mexico and therefore this work would represent one of the first studies of this subject and one of the first studies in the general field of Mexican scientific history.