Chapter 4 Inheritance analysis of fine structure of gene

• Concepts of genes• Recombination test• Complementation test • Deletion mapping• Split genes and overlapping genes• Function of genes

第四章 基因精细结构的遗传分析

• 一、基因的概念 • 二、重组测验 • 三、互补测验 • 四、缺失作图• 五、断裂基因与重叠基因• 六、基因的功能

4.1 Concepts of genes

• Development of concepts of genes

• 1. Genetic factors • 2. The Chromosome is the vecto

r of genes• 3. DNA is the hereditary materia

l • 4. Gene is the functional DNA

fragment• 5. The operon model• 6. Jumping genes and split gene

s

第一节 基因的概念

• 基因概念的发展• 1 、遗传因子 • 2 、染色体是基因的载体 • 3 、 DNA 是遗传物质 • 4 、基因是有功能的 DN

A 片段 • 5 、操纵子模型 • 6 、跳跃基因和断裂基 因

Gene types and their relationship)( 基因的类别及其相互关系 )

4.2 Recombinant test Pseudoalleles

The functional alleles located at the same locus, belonging to the different sites, can exchange each other and are closely linked

第二节 重组测验 -- 拟等位基因

• 拟等位基因：• 位于同一基因

座，属于不同基因位点，它们之间可发生交换这种紧密连锁的功能性等位基因

Recombinant test—Phage mutant 重组测验—噬菌体突变型

Benzer’ recombinant test Benzer 的重组测验

4.3 Complementation test 互补测验

4.4 Deletion Mapping-The tenet and method of deletion mapping

• The tenet of deletion mapping• The point mutation occurs a single site and the deletio

n mutation does a lot of sites. The former is reversible while the latter is irreversible. There existed the recombination between point mutations. However, it is impossible for between the deletion and point mutation which locates the deletion region to recombine.Therefore, the mutation site must be in the deletion region if it can not be recombined. Contrarily, the site must be not in the deletion region if it can be recombined

第四节 缺失作图 --- 缺失作图原理和方法

• 缺失作图原理• 点突变是单个位点的突变，缺失突变是多个位点

的突变；点突变可以发生回复突变，而缺失突变则是不可逆的；点突变与其他点突变之间可以发生重组而缺失突变同另一个（染色体同一）基因组内缺失区的点突变之间不可能重组。据此，凡是不能重组的，它的位置一定在缺失范围内，凡能和某一缺失突变体进行重组的，它的位置一定不在缺失范围内

Deletion Mapping-The tenet and method of deletion mapping

• Method of deletion mapping• Deletion phage mutant + r (cultivated in tⅡ

he strain B, E coli ) →take a drop to infect the strain K(A), E coli. If plaque is produced

in the strain K(A), wild plaque is produced b

y recombining between the two phages→ r mutant is not in dⅡ eletion phage

• 二 缺失作图方法：• 缺失型噬菌体 +rⅡ 突变型噬菌体（大肠杆菌 B

菌株中培养）→取一滴感染大肠杆菌 K(A) 菌株，若在 K(A) 菌株中形成噬菌斑，则说明它们之间发生了重组产生野生型噬菌斑→ rⅡ 突变型不在缺失型噬菌体范围内

Deletion mapping缺失作图

4.4 Split Gene断裂基因

exon and intron ( 外显子与内含子 )

Overlapping genes

• Sanger found ： ФХ174 including 5386 bp→9 genes→2000 amino acid→6000 bp →overlapping genes

• Overlapping mode:• Small genes within the big gene• overlapping between two genes• Triple overlapping between three genes• Anti- overlapping• Overlaping operon

重叠基因

• Sanger ：发现 ФХ174 有 5386 bp→9 个基因→ 2000 →氨基酸 6000 bp → 重叠基因

• 重叠方式：• 大基因内包含小基因• 前后两基因首尾重叠• 3 个基因间三重重叠• 反向重叠• 重叠操纵子

4.6 Gene Function

• DNA (gene) →mRNA →Polypeptide(amino acids and their linear arrangement) → Structure protein or enzyme → Chemical materials in the cell →Phenotype of tissues and organs→ Morphological characters of the organism

第六节 基因的功能• DNA （基因）→

mRNA→ 多肽（氨基酸种类和线性排列）→结构蛋白或酶→细胞内化学物质→细胞表型→组织器官表型（各部分表型）→生物的形态特征

One gene-one enzyme hypothesis

Phenylketonuria ： Phenylalanine Hydroxylase Traits in the organism result from a serial of bioche

mistry reactions catalyzed by enzymes, which are controlled by genes; that is, the function of genes. It showed that the traits are controlled by a lot of genes not one gene. The hypothesis of one gene-one enzyme shouled be modified with that of one gene-one protein, accutately, one gene-one polypeptide

一个基因一种酶假说

• 苯丙酮尿症（ PKU ）：苯丙氨酸羟化酶• 基因的功能是通过酶控制生化反应从而控制生物

性状的，从而也说明生物的性状往往是受一系列基因所控制的绝不是“一个基因一个性状”，至于 Beadle 和 Tatum 的“一个基因一个酶”的假说也须修改，而说成“一个基因一个蛋白质”，进而又提出“一个基因一条多肽链“

Evidence of one polypeptide- one gene

Sickle cell anemia in humans Hemoglobin consisted of 4 polypeptides ( ａ 2β2 ), glu

tamic acid in βchain is changed into valine

Normal genetype: HbA Hb

A （ HbA hemoglobin)

The sick genetype: HbS Hb

S （ HbS hemoglobin)

一个结构基因一条多肽链的证据

人的镰刀细胞贫血症

构成血红蛋白的 4 条多肽链（ａ 2β2 ）中的 β 链第六位氨基酸由正常的谷氨酸变成了缬氨酸

正常： HbA Hb

A 基因型（ HbA 血红蛋白）

患者： HbS Hb

S 基因型（ HbS 血红蛋白）