Agarose(琼脂糖) (1)a much less resolving 3 kb power than 2 kb polyacrylamide (2)but can separate DNA 0.5lb molecules of up to tens of kb
12 Agarose (琼脂糖): (1)a much less resolving power than polyacrylamide, (2)but can separate DNA molecules of up to tens of kb 1 kb 0.5 kb 2 kb 3 kb 4 kb
Pulsed- field gel electrophoresis(脉冲 电泳) (1)The electric field is applied in pulses that are oriented orthogonally(直角地) to each other (2) Separate DNA molecules according to their molecule weight, as well as to their shape and topological properties (3) Can effectively separate dna molecules over 30-50 kb and up to several Mb in length 13
13 (1)The electric field is applied in pulses that are oriented orthogonally (直角地) to each other. (2)Separate DNA molecules according to their molecule weight, as well as to their shape and topological properties. (3)Can effectively separate DNA molecules over 30-50 kb and up to several Mb in length. Pulsed-field gel electrophoresis (脉冲 电泳)
electrodes B Fig。20-2 pulsed field gel electrophoresis Switching between two orientations the larger the DNA is the longer it takes to reorient B Copyright@ 2004 Pearson Education, Inc, publishing as Benjamin Cummings
14 Fig. 20 -2 pulsed - field gel electrophoresis Switching between two orientations: the larger the DNA is, the longer it takes to reorient
Electrophoresis is also used to separate RNAs (1)RNA have a uniform negative charge as DNA does (2)RNA is single-stranded and have extensive secondary and tertiary structure, which significantly influences their electrophoretic mobility (3)RNA can be treated with reagent such as glyoxal(乙二醛) to prevent rNa base pairing, so that its mobility correlates with the molecular weight
15 (1)RNA have a uniform negative charge as DNA does. (2)RNA is single-stranded and have extensive secondary and tertiary structure, which significantly influences their electrophoretic mobility. (3)RNA can be treated with reagent such as glyoxal (乙二醛) to prevent RNA base pairing, so that its mobility correlates with the molecular weight Electrophoresis is also used to separate RNAs
Nucleic acids-Restriction digestion 2. Restriction endonucleases(限制 性内切酶) cleave dna molecules at particular sites a Why use endonucleases? --To make large dNa molecules break into manageable fragments. 16
16 2. Restriction endonucleases (限制 性内切酶) cleave DNA molecules at particular sites ◼ Why use endonucleases? --To make large DNA molecules break into manageable fragments. Nucleic acids-Restriction digestion