6.2 接合.ppt
《6.2 接合.ppt》由会员分享,可在线阅读,更多相关《6.2 接合.ppt(24页珍藏版)》请在得力文库 - 分享文档赚钱的网站上搜索。
1、Conjugation(接合接合):the second mechanism thatbacteria use to exchange genesE.Coli-the ultimate lab rat Plasmid(质粒质粒):Extrachromosomal genetic elements that are capable of autonomous replication(replicon)(1)Extrachromosomal DNA,usually circular(2)Usually encode ancillary functions for in vitro growth.(
2、3)Can be essential for specific environments:virulence,antibiotics resistance,use of unusual nutrients,production of bacteriocins(细菌素).(4)Must be a replicon-self-replicating genetic unit.Classification of Plasmids(1)Conjugative plasmid Carries genes for sex pili and transfer of the plasmid,F plasmid
3、(2)Dissimilation plasmids Encode enzymes for catabolism of unusual compounds(3)R factor Encode antibiotic resistanceFigure 8.29有性纤毛基因:PilusConjugative plasmidF plasmid(1)large(100 kb)(2)low copy(1-2 copies/cell)(3)self transmissible(传递)(4)requires protein synthesis RepE gene encodes RepE protein Rep
4、E protein binds to origin of replication and initiates DNA replication.RepE binds to the repE promoter and activates transcription.Bacterial PhenotypesBacterial Cells Can RecombineDiscovered by Lederberg and Tatum(40s)野生的野生的Bacterial Cells Can RecombineWhy did they use multiple different mutations?R
5、ecombination Requires Physical ContactThis shows that it is not the transfer of a molecule through the medium过滤器过滤器 Recombination Requires Physical ContactThe process is called congugation(接合接合),and it involves the transfer of a plasmid(F factor)from one cell to anotherF Factor Integration Yields Hf
6、r StrainsIf the F factor integrates at random points in the chromosome Hfr(high frequency of recombination)strains are generated.Episome(附加体附加体):a plasmid that can integrate into the chromosomeTransferred DNA May RecombineBut the transfer is unidirectional,unlike eukaryotic sex.Partial diploid(部分二倍部
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 6.2 接合
限制150内