第四章细菌的遗传分析
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(只有偶数次交换才能保证细菌染色体的完整性，产生 平衡的有活性的重组子；重组子只有一种类型， 相反 的重组子不会出现）
◇ Recombination mapping
Hfr lac+ade+ Strs × F－ lac－ade－ Strr
根据中断杂交试验，已知lac和ade紧密连锁，且 lac先于ade进入F－
To produce recombination cells, there must be an even number of crossovers.
Only one product of recombination survives. The reciprocal exchange product is generally lost in subsequent cell growth.
中断杂交图是以基因转移的先后顺序为依据， 基因间距离以转移时间（min）为单位绘制的, 对于紧密连锁的基因无法定位
一般选择距离在2min内的基因进行重组作图 中断杂交图1min的图距相当于重组图中的20
第四章 细菌的遗传分析
Focus on E.coli
第一节 细菌的接合 （Bacterial conjugation)
1. The experiments done by Lederberg and Tatum 1940s
2. The F plasmid and conjugation (F质粒与接合）
2. Recombination mapping
Interrupted mating experiments cannot distinguish the relative positions of genes within about 2 minutes of each other and thus give only a crude idea of gene location.
在含有链霉素的基本培养基上筛选ade+strr ，再影 印到EMB培养基上检测重组子类型
紫红色菌落：
lac+ade+ 780（亲本型）
白色或粉红色菌落： lac－ade+ 220（重组型）
Donor: lac＋ade ＋ Recipient: lac－ade－
Progeny
Parental:
lac＋ade ＋
Recombination analyses of Hfr crosses improve mapping accuracy
◇ Property of bacterial recombination
A single crossover( or odd number) would be lethal because the ring is broken to produce a strange, partly diploid linear chromosome
lac－ade－
Recombinant: lac＋ade－
lac－ade＋
lac－ade+ RF(lac-ade)= (lac－ade+)+ (lac+ade+)
3. The relationship of interrupted mating mapping and recombination mapping
Formation of an F’ plasmid
Sex conduction
merozygote
Using F’ plasmid for complementation analysis
5. Summary of conjugation in E.coli
ห้องสมุดไป่ตู้
第二节 中断杂交实验与重组作图
TraS和TraT编码“表面排斥”蛋 白，使F+与F+细胞不能结合
3. High frequency recombination (Hfr) bacteria and the transfer of chromosomal genes (高频重组菌株与染色体转移)
Because the transfer is usually interrupted in the midstream, the second half of the F plasmid is not transferred. Only about 1/10000 Hfr cells transfers an entire strand of its chromosome to a recipient F－ cell
Plasmids: smaller cycles of double-strand DNA that do not carry essential genes
F plasmid (sex factor, fertility factor)
F+×F－接合，95%的F－转变为F+， 染色体上基因重组频率极低
transferred genes
azir azir tonr azir tonr lac+ azir tonr lac+ gal+
Comparisons of interrupted mating studies using different Hfr strains confirm that the bacterial chromosome is a circle
Interrupted mating experiment and recombination mapping
In the mid-1950s Ellie Wollman & Francois Jacob
1. Interrupted mating experiment
time (min) ＜9 9 11 18 24
▪ DNA from the donor will be lost unless it is incorporated into the recipient’s chromosome through a double recombination
4. F’ plasmid and sex conduction F’ 质粒和性导
◇ Recombination mapping
Hfr lac+ade+ Strs × F－ lac－ade－ Strr
根据中断杂交试验，已知lac和ade紧密连锁，且 lac先于ade进入F－
To produce recombination cells, there must be an even number of crossovers.
Only one product of recombination survives. The reciprocal exchange product is generally lost in subsequent cell growth.
中断杂交图是以基因转移的先后顺序为依据， 基因间距离以转移时间（min）为单位绘制的, 对于紧密连锁的基因无法定位
一般选择距离在2min内的基因进行重组作图 中断杂交图1min的图距相当于重组图中的20
第四章 细菌的遗传分析
Focus on E.coli
第一节 细菌的接合 （Bacterial conjugation)
1. The experiments done by Lederberg and Tatum 1940s
2. The F plasmid and conjugation (F质粒与接合）
2. Recombination mapping
Interrupted mating experiments cannot distinguish the relative positions of genes within about 2 minutes of each other and thus give only a crude idea of gene location.
在含有链霉素的基本培养基上筛选ade+strr ，再影 印到EMB培养基上检测重组子类型
紫红色菌落：
lac+ade+ 780（亲本型）
白色或粉红色菌落： lac－ade+ 220（重组型）
Donor: lac＋ade ＋ Recipient: lac－ade－
Progeny
Parental:
lac＋ade ＋
Recombination analyses of Hfr crosses improve mapping accuracy
◇ Property of bacterial recombination
A single crossover( or odd number) would be lethal because the ring is broken to produce a strange, partly diploid linear chromosome
lac－ade－
Recombinant: lac＋ade－
lac－ade＋
lac－ade+ RF(lac-ade)= (lac－ade+)+ (lac+ade+)
3. The relationship of interrupted mating mapping and recombination mapping
Formation of an F’ plasmid
Sex conduction
merozygote
Using F’ plasmid for complementation analysis
5. Summary of conjugation in E.coli
ห้องสมุดไป่ตู้
第二节 中断杂交实验与重组作图
TraS和TraT编码“表面排斥”蛋 白，使F+与F+细胞不能结合
3. High frequency recombination (Hfr) bacteria and the transfer of chromosomal genes (高频重组菌株与染色体转移)
Because the transfer is usually interrupted in the midstream, the second half of the F plasmid is not transferred. Only about 1/10000 Hfr cells transfers an entire strand of its chromosome to a recipient F－ cell
Plasmids: smaller cycles of double-strand DNA that do not carry essential genes
F plasmid (sex factor, fertility factor)
F+×F－接合，95%的F－转变为F+， 染色体上基因重组频率极低
transferred genes
azir azir tonr azir tonr lac+ azir tonr lac+ gal+
Comparisons of interrupted mating studies using different Hfr strains confirm that the bacterial chromosome is a circle
Interrupted mating experiment and recombination mapping
In the mid-1950s Ellie Wollman & Francois Jacob
1. Interrupted mating experiment
time (min) ＜9 9 11 18 24
▪ DNA from the donor will be lost unless it is incorporated into the recipient’s chromosome through a double recombination
4. F’ plasmid and sex conduction F’ 质粒和性导