乳糖操纵子LactoseOperonforgraduatestudents.ppt
《乳糖操纵子LactoseOperonforgraduatestudents.ppt》由会员分享,可在线阅读,更多相关《乳糖操纵子LactoseOperonforgraduatestudents.ppt(10页珍藏版)》请在三一文库上搜索。
1、乳糖操纵子 Lactose Operon for graduate students,牛登科 生命科学学院 2010年10月,Lactose Operon,Structural genes lac z, lac y, & lac a Promoter Polycistronic mRNA Regulatory gene Repressor Operator Operon Inducer - lactose,Lactose Operon,Inducer - lactose Absence Active repressor No expression,Presence Inactivation o
2、f repressor Expression,Negative control,Is the story complete?,These two pages are copied from the PPT of an American teacher. Has your textbook told you something more? If no, are you satisfied with this theory? No lactose, no genes transcribed, no proteins produced, and then nothing to transport l
3、actose into the cell. A dead cycle,Basal transcription,The repressor could not entirely repress the genes. In absence of lactose, there is a low level of leaky gene expression of lactose operon genes. The negative control of lactose operon is not yes or no, but more or less. In fact, in eukaryotes,
4、there are also many genes that are transcribed and translated, at low levels, in the cells that obviously do not need them. And the reason for this is not clear, awaiting for you to discover.,Do you still have any question?,Why operon? Operons contain genes belonging to the same functional pathway i
5、n order to guarantee them a similar expression level. About half of the protein-coding genes are organized in operons. However, prokaryotic genomes are rather unstable and only 525% of genes belong to strings shared by at least two distantly related species. The biological significance and mechanism
6、(s) of operon formation are still under debate. At least seven different models have been proposed for operon formation. For details, see Res. Microbiol. 160: 502-512, 2009.,More questions?,Why negative control? That is, is there any trouble if the lactose operon genes are constitutively expressed?
- 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:
- 乳糖 操纵子 LactoseOperonforgraduatestudents
链接地址:https://www.31doc.com/p-2578233.html