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Chapter 23 Transposition(转座)
23.1 Bacterial Transposons(转座子) Transposition,a transposable element, or transposon,moves from one DNA address to another
23.1 Bacterial Transposons (转座子) Transposition, a transposable element, or transposon, moves from one DNA address to another
Transposable elements in prokaryotes: Three examples: l.Insertion sequence(IS插入序列)elements 2.Transposons(Tn,转座子) 3.Bacteriophage Mu(Mu phage,转座噬菌体)
Transposable elements in prokaryotes: Three examples: 1. Insertion sequence (IS插入序列) elements 2. Transposons (Tn,转座子) 3. Bacteriophage Mu (Mu phage,转座噬菌体）
Discovery of Bacterial Transposons phage mutations the mutant genes contained long stretches of extra DNA. Phage Phage λ入(gal+) 入(gal-) gal-phage gal+phage lyticlytic(裂解)infection Ultracentrifuge Collect fractions explanation High Low density density foreign DNA had inserted into the gal gene and thereby mutated it.Indeed, nsertion later experiments revealed 800-1400- bp inserts in the mutant gal gene->insertion sequences (ISs)
Discovery of Bacterial Transposons phage mutations : the mutant genes contained long stretches of extra DNA. lyticlytic(裂解)infection foreign DNA had inserted into the gal gene and thereby mutated it. Indeed, later experiments revealed 800-1400- bp inserts in the mutant gal gene→insertion sequences (ISs). explanation :
Insertion Sequences(lSs,插入序列)： The Simplest Bacterial Transposons ISs contain only the elements necessary for transposition. 1.inverted terminal repeats (ITRs)at a transposon's ends,one of which is the inverted repeat of the other. 2.The set of genes(at least two)that code for the enzymes that catalyze transposition(transposase,转座酶). Insertion sequence,IS1 R Transposase gene IR 5'GGTGATGCTGCCAACTTACTGAT 3 5'ATCAATAAGTTGGAGTCATTACC 3 3 CCACTACGACGGTTGAATGACTA 5 3 TAGTTATTCAACCTCAGTAATGG 5
Insertion Sequences(ISs,插入序列): The Simplest Bacterial Transposons ISs contain only the elements necessary for transposition. 1. inverted terminal repeats (ITRs) at a transposon‘s ends, one of which is the inverted repeat of the other. 2.The set of genes(at least two)that code for the enzymes that catalyze transposition (transposase,转座酶)