2)Hf×F杂交 Hfr菌株的F因子插入到染色体DNA上,因此只要发生接合转移过程,就可以把 部分甚至全部细菌染色体传递给F细胞并发生重组,由此而得名为 高频重组菌株(Hfr) Transfer to F recipient A E D C B Figure 9. 25 Integration of an F plasmid into the chromo- some with the formation of an Hfr. The insertion of the F plasmid occurs at a variety of specific sites where IS ele- ments are located, the one here being between chromosomal genes pro and lac. The letters on the F plasmid represent arbi trary genes. The arrow indicates the origin of transfer, with the arrow as the lead which pairing with the chromosome occurs is between A and Figure 9 26 Breakage of the Hfr chromosome at the origin B. Thus, in this Hfr pro would be the first chromosomal gene d transfer of DNA to the recipient. Replication occurs dur- to be transferred and lac would be among the last ing transfer, as illustrated in Figure 9.23 17
Hfr菌株的F因子插入到染色体DNA上，因此只要发生接合转移过程，就可以把 部分甚至全部细菌染色体传递给F-细胞并发生重组，由此而得名为 高频重组菌株（Hfr） 2）Hfr ×F -杂交 17
染色体上越靠近F因子的先导区的基因,进入的机会 就越多,在F中出现重组子的时间就越早,频率也高。 Hfr F Hfr菌株与F十:都有性菌毛,与F细胞进行 接合。 区别是:Hfr×F杂交后的受体细胞或接合 子)大多数仍然是F。 Tn7000 1000 1s2 F 75 inc, rep, oris, phi Figure 9.19 Genetic map of the F (fertility) plasmid of
染色体上越靠近F因子的先导区的基因，进入的机会 就越多，在F-中出现重组子的时间就越早，频率也高。 18 Hfr菌株与Ｆ＋：都有性菌毛，与F-细胞进行 接合。 区别是：Hfr×F-杂交后的受体细胞(或接合 子)大多数仍然是F—
3)F×F杂交 incuding part of bacterial chromo son Hfr菌株内的F因子因不 正常切割而脱离染色体 时,形成游离的但携带 小段染色体基因的F 因子,特称为F因子。 F'XF与F×F的不同:给体的部分染色体基因随 F'一起转入受体细胞 a)与染色体发生同源重组; F plasmid replicate b)继续存在于F因子上, 形成一种部分二倍体; F因子传递基因,也叫性导,mm ajugation. (a) Due to an error in excision, the A 或F因子转导 factor. (b) The A gene is then transferred to a recipient dun (b)
3）F′×F-杂交 Hfr菌株内的F因子因不 正常切割而脱离染色体 时，形成游离的但携带 一小段染色体基因的F 因子，特称为F′因子。 F′×F-与F+×F-的不同：给体的部分染色体基因随 F′一起转入受体细胞 a）与染色体发生同源重组； b）继续存在于F′因子上， 形成一种部分二倍体； 19 F′因子传递基因，也叫性导， 或Ｆ因子转导
Q需 十 分离或消除 与 脱整 接 离 不正常脱离 Hfr
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Lederberg coined the term pl plasmid in th e 1950s to describe such apparently extrachromosomal genetic elements, although it did not find wide usage until the 1970s when infectious drug resistance become a medical problem, and genetic engineering become popular
Lederberg coined the term plasmidin the 1950s to describe such apparently extrachromosomal genetic elements, although it did not find wide usage until the 1970s when infectious drug resistance become a medical problem, and genetic engineering become popular. 21