遗传学课件-核外遗传.pptVIP

2）叶绿体DNA的物理图谱和基因组成 大量植物叶绿体限制性酶切图谱和全序列测序分析表明它们几乎含有相同的叶绿体基因组成。 Wheat mesophyll cell has 16000–26000 copies of cpDNA. This makes 5–7% of the cellular DNA in the mesophyll cell. The wheat chloroplast genome, like all other plant chloroplast genomes, has two inverted repeat regions, each copy (21-kb-long) separated from the other by two single copy regions (12.8 kb, 80.2 kb). 陆生植物叶绿体基因组编码的总基因数目: 105-113 2、叶绿体遗传的表现 1）紫茉莉花斑枝条遗传： 部分 2）、玉米条纹叶的遗传： 二、 线粒体（Mitochondrion）遗传及分子基础 1、线粒体基因组的一般性质 2、线粒体DNA组成 1）mtDNA主要编码rRNA和tRNA分子、氧化呼吸所需要的酶类等少部分亚基。 2）哺乳动物的线粒体基因没有内含子 Wheat mtDNA is larger (430 kb) than cpDNA (135 kb) but encodes only 30–50% polypeptides relative to cpDNA. Thus, large amount of mtDNA is noncoding, there being about 55 genes involved in RNA synthesis. 4）某些蛋白质的密码子与核基因通用密码子不同 3)与核DNA相比，mtDNA作为生物体种系发生的“分子钟”(molecular clock) 3、The evolutionary origin of organelles A wide accepted theory holds that eukaryotic organelles originally evolved from prokaryotes that lived inside primitive cells in symbiosis, a mutually beneficial interaction. This is called endosymbiont theory(内共生理论) 1970，Margulis，真核细胞祖先是某种吞噬细胞:线粒体祖先是种革兰氏阴性细菌;而叶绿体祖先是蓝细菌。 细胞分化假说：原始的原核细胞质膜内陷包被DNA，然后再分化形成独立的细胞器。 4、小菌落链孢霉 (Neurospora) 的遗传 1952年Mary Mitchell 分离到链孢霉的小菌落（poky），并杂交实验： poky♀×野生型♂→后代全部为poky； 野生型♀×poky♂→后代全部为野生型。 不符合孟德尔遗传，认为受细胞质遗传物质控制，称之为核外突变（extranuclear mutation） 或细胞质突变（cytoplasmic mutation） Explanation of the different results from reciprocal crosses（正反交） of poky and normal Neurospora： The parent contributing most of the cytoplasm of the progeny cells is called female. Brown shading represents cytoplasm with the poky determinants. 反交 正交 The Poky mutation resides in the mitochondrial genome?： It disrupts the production of cytochromes, it is slow growing, and it has abnormal amounts of mitochondrial cytochrome proteins. Like most organisms, wild-type Neurospora has three main types of cytochrome: a, b, and c . Poky, however, lacks cytochromes a and b and