electrodes Electrophoresis A B pulsed-field gel electrophoresIs Switching between two orientations: the larger the DNA is, the longer it takes to reorient B A Copyright C 2004 Pearson Education, Inc, publishing as Benjamin Cummings
11 pulsed-field gel electrophoresis Switching between two orientations: the larger the DNA is, the longer it takes to reorient Electrophoresis
Restriction digestion Restriction endonucleases 2 cleave dna molecules at o. particular sites e a Why use endonucleases? To make large dNA molecules break into manageable fragments 12
12 Restriction endonucleases cleave DNA molecules at particular sites Nucleic acid ◼ Why use endonucleases? --To make large DNA molecules break into manageable fragments Restriction digestion
Restriction digestion Restriction endonucleases: the nucleases that cleave dna at particular sites by the recognition of specific sequences a The target site recognized by endonucleases is usually palindromic〔回文结构)。 eg。EcoR 5..GAATTC.3 CTTAAG 13
13 ◼ Restriction endonucleases: the nucleases that cleave DNA at particular sites by the recognition of specific sequences ◼ The target site recognized by endonucleases is usually palindromic (回文结构). e.g. EcoRI 5’….GAATTC.….3’ ….CTTAAG…. Restriction digestion
Restriction digestion To name a restriction endonuclease e. g ECORI the 1st such Escherichia coli R13 enzyme found Species category strain 14
14 ◼To name a restriction endonuclease: e.g. EcoRI the 1st such enzyme found Escherichia coli Species category R13 strain Restriction digestion
Restriction digestion -Frequency of the occurrence of hexameric sequence 1/4096(4-6) Randomly 15
15 ◼Frequency of the occurrence of hexamaeric sequence: 1/4096 (4-6) Randomly Restriction digestion