14 public questions tagged with this topic.
Gel electrophoresis is used to separate DNA fragments based on size using an electric field.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Processes - Isolation of DNA and Gel Electrophoresis
Smaller DNA fragments migrate faster through the gel than larger fragments due to their lower resistance.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Processes - Isolation of DNA and Gel Electrophoresis
Smaller DNA fragments migrate faster through the gel than larger fragments due to lower resistance.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Processes - Isolation of DNA and Gel Electrophoresis
DNA is negatively charged and moves toward the positive electrode (anode) in gel electrophoresis, not the negative electrode.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Processes - Isolation of DNA and Gel Electrophoresis
DNA is negatively charged and moves toward the positive electrode (anode) in gel electrophoresis.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Processes - Isolation of DNA and Gel Electrophoresis
DNA is negatively charged and moves toward the positive electrode (anode) in gel electrophoresis, not the negative electrode.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Processes - Isolation of DNA and Gel Electrophoresis
In gel electrophoresis, DNA fragments are separated based on size, with smaller fragments migrating faster than larger ones.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Processes - Isolation of DNA and Gel Electrophoresis
Gel electrophoresis is used to separate DNA fragments based on size, with smaller fragments migrating faster in the gel.
Ref: NCERT Class 12 Biology Chapter 9: Biotechnology: Principles and Processes Processes - Isolation of DNA and Gel Electrophoresis
CsCl density gradient centrifugation uniquely separates DNA species based on conformation and buoyant density in an isopycnic gradient. Supercoiled, nicked, and linear DNA differ in capacity to intercalate EtBr, resulting in distinct buoyant densities and band positions. Silica columns and magnetic beads purify by adsorption based on chemical interaction with matrix, not conformation. GITC lysis denatures proteins for extraction but does not resolve topology. Therefore only CsCl centrifugation discriminates DNA forms by supercoiling, linking conformational state to measurable density differences for high-resolution purification of plasmids.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
In alkaline lysis for plasmid isolation, covalent closed circular supercoiled plasmid DNA and linear chromosomal DNA behave differently due to topology. Under alkaline conditions with SDS, both are denatured. Upon rapid neutralization, small supercoiled plasmids renature quickly because their two strands remain interlinked topologically, becoming soluble. Large chromosomal fragments cannot correctly reanneal and form an insoluble network with SDS-protein complexes and precipitate. Thus separation is based on topological differences and renaturation kinetics, not merely size variation or charge differences alone.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
Phenol-chloroform extraction separates nucleic acids based on differential solubility. Phenol denatures proteins and chloroform improves phase separation and removes lipids. When mixed with aqueous lysate and centrifuged, two phases form: lower organic phase containing phenol-chloroform and hydrophobic molecules, and upper aqueous phase containing hydrophilic nucleic acids. DNA, being highly polar due to its phosphate backbone, remains soluble in the aqueous phase, while denatured proteins partition into organic phase or precipitate at interphase. Thus pure DNA is recovered from the aqueous layer for subsequent precipitation.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
In manual Sanger sequencing, termination products from synthesis reactions must be ordered by size to deduce sequence. Denaturing polyacrylamide gel electrophoresis provides single-nucleotide resolution due to its highly crosslinked matrix with small pore size, unlike agarose. Fragments migrate inversely to length; shorter fragments run faster and appear at bottom. By running four lanes or four colors in capillary, the ladder reveals base order. Polyacrylamide does not precipitate DNA, detect bases or primarily buffer pH. Its purpose is size separation with near single-base precision essential for accurate sequence reading.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
