课件：DNA重组

1、H2A,H4,H2B,H3,H2A,H4,H2B,H3,H4,H4,H2B,H2B,H2A,H3,H3,(a) (b),Core histones,+,+,+,+,+,H3,Nucleosome,Octamer,DNA strand,Two of each core histone come together to form an octamer; The negative charges on DNA are attracted to the positive charges on the histones. DNA is wrapped around a core of histone t

2、o form a nucleosome.,2 nm,11 nm,30 nm,300 nm,700 nm,1400 nm,A heteroduplex,Crossing over,Pairing of homologous chromosomes,Crossing over is not as simple as cutting and pasting. Chromosomal regions are connected by a heteroduplex joint after crossing over.,DNA RECOMBINATION,A BRIEF INTRODUCTION OF H

3、OLLIDAY MODEL A BRIEF INTRODUCTION OF TRANSPOSON,Four cuts are made as indicated by the arrows,Molecule flipping and gap sealing,Resolution of the Holliday junction to create a crossover,Pairing of homologous chromosomes,Barbara McClintock,activator element,dissociation element,GTACCATGATG CATGGTACT

4、AC,GTACCATGAT C-3,3-G ATGGTACTAC,GTACCATGAT C,G ATGGTACTAC,GTACCATGAT CATGGTACTA,TACCATGATG ATGGTACTAC,Make staggered cuts at target site,Insert transposon,Repair synthesis and seal gaps,Direct repeats,Simplified mechanism of transposition,GGTACTCTCC CCATGAGAGG,AATCGCGG TTAGCGCC,CCGCGATT GGCGCTAA,GGTACTCTCC CCATGAGAGG,Insert sequence,Direct repeats,Inverted repeats,Genes coding for transposase,General structure of insertion sequences (transposon),Transposons are also called MGE (Mobile Genetic