Figure 20-1 DNA separation by gel electrophoresis electrophoresis chamber buffer solution DNA fragments agarose gel electrode electrode electrode electrode small DNA fragments move further through the gel than large fragments Copyright o 2004 Pearson Education, Inc, publishing as Benjamin Cummings
Figure 20-1 DNA separation by gel electrophoresis
After electrophoresis is complete DNA molecules can be visualized by staining the gel with fluorescent dyes( such as ethidiun溴化 乙锭)
After electrophoresis is complete: DNA molecules can be visualized by staining the gel with fluorescent dyes(such as ethidium溴化 乙锭)
Two alternative kinds of gel matrices. > Polyacry/ amide(聚丙烯酰胺): has high resolving capability but can separate DNAs only over a narrow size range Can resolve dNAs that differ from each other in size by as little as a single base pair but only with molecules of up to several hundred base pairs > Agarose(琼脂糖) has less resolving power than polyacrylamide but can separate from one another dNa molecules of up to tens, and even hundreds, of kilobases
Two alternative kinds of gel matrices: ➢Polyacrylamide(聚丙烯酰胺):has high resolving capability but can separate DNAs only over a narrow size range. Can resolve DNAs that differ from each other in size by as little as a single base pair but only with molecules of up to several hundred base pairs. ➢Agarose(琼脂糖)has less resolving power than polyacrylamide but can separate from one another DNA molecules of up to tens,and even hundreds,of kilobases
Pulsed-field gel electrophoresis(脉冲电场凝胶 电泳 very long DNAs be resolved from one another if the electric field is applied in pulses that are oriented orthogonally to each other. figure20-2
Pulsed-field gel electrophoresis(脉冲电场凝胶 电泳)very long DNAs be resolved from one another if the electric field is applied in pulses that are oriented orthogonally to each other.figure20-2
Each time the orientation of the electric field changes, the DNA molecule snaking its way through the gel, reorient to the direction of the new field. the larger the dna, the longer it takes to reorient This can be used to determine the size of entire bacterial chromosomes and chromosomes of lower eukaryotes
Each time the orientation of the electric field changes,the DNA molecule,snaking its way through the gel,reorient to the direction of the new field.the larger the DNA,the longer it takes to reorient. This can be used to determine the size of entire bacterial chromosomes and chromosomes of lower eukaryotes