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1、第 4 节 核酸与基因Concept of Nucleic acid and the Gene一 基因的概念早期的基因概念 经典的基因概念 基因概念的演变与发展 基因的分子结构 基因概念的多样性 融合遗传理论 （Blending inheritane）母本体液 父本体液 子代具有父，母双亲的性状 + 获得的性状是由环境影响 (非遗传物质的改变) 新性状一旦获得, 便能遗传给后代L.B.Lamarck获得性遗传理论(Inheritance of acquired characters) 物种 加强和完善对环境的适应 逐渐转变为新种泛生论假说 （Hypothesis of the Pangenes
2、is） C. Darwin 1868 种质论（Theory of germplasm）Germeplasm SomatoplasmRoot, Stem, LeafA.Weismann 1883. Somatoplasm Germplasm Germplasm孟德尔 (1823-1884)“遗传学之父” 阐述了遗传学的分离和自由组合两大定 律，以及“基因”的概念。Mendels Paper in English Experiments in Plant Hybridization (1865) by Gregor MendelRead at the meetings of February 8t
3、h, and March 8th, 1865 1 Introductory Remarks Experience of artificial fertilization, such as is effected with ornamental plants in order to obtain new variations in color, has led to the experiments which will here be discussed. The striking regularity with which the same hybrid forms always reappe
4、ared whenever fertilization took place between the same species induced further experiments to be undertaken, the object of which was to follow up the developments of the hybrids in their progeny.遗传因子假说 (Hypothesis of the inherited factor) G. J. Mendel 1866. 生物性状由遗传因子控制 亲代传给子代的是遗传因子(A,a.) 遗传因子在体细胞内成
5、双(AA,aa),在生殖细胞内为单（A,a） 杂合子后代体细胞内具有成双的 遗传因子(Aa) 等位的遗传因子独立分离, 非等 位遗传因子间自由组合地分配到配子中摩尔根：阐述了遗传学的连锁与交换定律，被誉为“现代实验生物学奠基人”。Theory of the gene 基因是染色体上的实体 基因象链珠(bead)一样，孤立地呈线状地排列在染色体上 基因是； 功能(functional unit)突变(mutation unit) 交换(cross-over unit) “三位一体”的 (Three in one) 最小的 不可分割的基本的遗传单位 (1926 T. H. Morgan) Tran
6、scriptable, translatable gene ( Z,Y,A ) Transcriptable but nontranslatable gene ( tDNA, rDNA )Nontranscriptable, nontranslatable gene ( promoter, operator ) Forms of genes cis action factorAffects the activity only of DNA sequences on its own molecular of DNA, this property usually implies that the
7、factor does not code for protein通过核苷酸自身的特异二级结构控制与它紧密连锁的结构基因的表达，一般不编码蛋白质。(无基因产物的DNA功能 区) Forms of genes trans action factor cis-dominant(显性)Affects the activity of any gene located on genome(基 因组) by its translated product.通过扩散自身表达产物（酶，调节蛋白）控制其他基因的表达可转录，可翻译调节蛋白的DNA功能区,可通过互补测验体系确定 其功能区域The ability of
8、a site (cis-factor) to control adjacent gene irrespective of the presence in the cell of other alleles(等位基因) of the site.cis acting factor 对与其紧密连锁基因的控制效应不受其等位基 因的影响。 DNA is genetic material Is the protein genetic material ?复制 ?表面遗传信息 ? RNA is genetic material also Tobacco Mosaic Virus (TMV) Hershey lambdar phage cycle Watson NYR多为Hydrophobic amino acid, 改变蛋白质性能 原始密码子多为 RNYRNYRNY ( A/G N U/C) RNYRNYRNY ( N Y R) (N A/G U/C) +1移码, 进化
