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#agarose gel

6 public questions tagged with this topic.

ZOOLOGY

Which of the following is used to extract and purify DNA fragments from an agarose gel?

Elution is the process of extracting DNA fragments from an agarose gel for further use in recombinant DNA experiments. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Zoology section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Zoology portion (Latest NCERT Textbooks for Academic Session 2026-27 - Rationalized Edition for Class XI and XII), Topic: Structural organization, physiology, human health and related concepts as per latest syllabus.

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Electrophoresis

What is the usual concentration range of agarose used in gels?

Agarose gel concentration determines pore size and resolving range. Common laboratory concentrations range from 0.7 percent for large 5 to 60 kb fragments to 2 percent for 100 to 3000 bp fragments. The typical routine range encompassing most plasmid analyses and restriction digests is 1 to 3 percent, balancing handling strength and resolution. Below 0.3 percent gels become too fragile, above 4 percent viscosity and EEO increase excessively. Thus 1 to 3 percent represents standard usage, though specialized applications may use 0.5 to 2.5 percent.

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.

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Electrophoresis

Electroendosmosis in agarose gels is due to:

Electroendosmosis is bulk fluid flow toward cathode opposite to DNA migration, caused by fixed charges on support matrix. Agarose contains residual sulfate and pyruvate groups introduced during purification from agar, imparting negative charge to gel fibers. Under electric field, counterions in diffuse layer move toward cathode, dragging water with them. This electroosmotic flow retards anionic DNA and causes band broadening. Highly purified low-EEO agarose minimizes this effect. Thus phenomenon originates not from pH or temperature alone, but from intrinsic charged substituents within agarose polymer.

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.

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Electrophoresis

What type of support matrix is used in zone electrophoresis?

Zone electrophoresis separates molecules into discrete zones or bands on a stabilizing support to minimize convection and diffusion. Early methods employed filter paper or cellulose acetate strips saturated with buffer, providing a solid anticonvective medium. Samples migrate as discrete zones under applied voltage. Glass and plastic are not porous supports for zone stabilization. Modern zone electrophoresis uses agarose or polyacrylamide gels as improved supports, but historically and categorically, paper represents the classic support matrix distinguishing zone electrophoresis from moving-boundary or free-flow electrophoresis.

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.

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Electrophoresis

Which of the following gel matrices is best suited for resolving DNA fragments ranging from 50 to 50,000 bp?

Agarose forms a porous matrix with large, tunable pore sizes determined by concentration, typically 0.7 to 2 percent. This range allows efficient sieving of DNA fragments from approximately 50 bp to over 50,000 bp, covering routine plasmids, restriction digests, and genomic DNA preparations. Polyacrylamide offers much smaller pores, ideal for 5 to 500 bp resolution at single-basepair discrimination. Cellulose acetate and thin-layer matrices lack molecular sieving for nucleic acids. Agarose provides low electroendosmosis, low UV absorption, and non-denaturing separation, making it the standard choice for broad-range DNA electrophoresis.

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.

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