20xx年醫(yī)學(xué)專題—5細(xì)菌的遺傳和變異e-預(yù)覽頁
【正文】 a bacterial infection. In Salmonella there are two genes which code for two antigenically different flagellar antigens. The expression of these genes is regulated by an insertion sequences. In one orientation one of the genes is active while in the other orientation the other flagellar gene is active. Thus, Salmonella can change their flagella in response to the immune systems39。,第十頁，共四十二頁。 alkylating agents 5bromouracil benzpyrene Radiation: Xrays and Ultraviolet light Viruses,第十三頁，共四十二頁。,第十六頁，共四十二頁。,第二十頁，共四十二頁。,Physiological States of F Factor,Integrated (Hfr) Characteristics of Hfr x F crosses F rarely becomes Hfr while Hfr remains Hfr High transfer of certain donor chromosomal genes,第二十三頁，共四十二頁。,Mechanism of F’ x F Crosses,DNA transfer Origin of transfer Rolling circle replication,Pair formation Conjugation bridge,第二十七頁，共四十二頁。,The mechanism of generalized transduction,第三十一頁，共四十二頁。,Generalized transduction,It is relatively easy. It is rather efficient (103 per recipient with P22HT, 106 with P22 or P1), using the correct phage. It moves only a small part of the chromosome which allows you to change part of a strain39。,Specialized transduction,Very efficient transfer of a small regioncan be useful for finestructure mapping Excellent source of DNA for the chromosomal region carried by the phage, since every phage carries the same DNA. Can often be used to select for deletions of some of the chromosomal genes carried on the phage. Merodiploids generated using specialized phage can be quite useful in complementation analyses.,第三十八頁，共四十二頁。,內(nèi)容(n232。Origin of tran
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