Given below are two statements :
Statement I : The DNA fragments extracted from gel electrophoresis

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Question

Given below are two statements :
Statement I : The DNA fragments extracted from gel electrophoresis can be used in construction of recombinant DNA.
Statement II : Smaller size DNA fragments are observed near anode while larger fragments are found near the wells in an agarose gel.
In the light of the above statements, choose the most appropriate answer from the options given below :
(1) Statement I is incorrect but statement II is correct
(2) Both statement I and statement II are correct
(3) Both statement I and statement II are incorrect
(4) Statement I is correct but statement II is incorrect

Accepted Answer

Correct Answer: B — Both statement I and statement II are correctStep-by-step Solution:Statement I Analysis: After agarose gel electrophoresis separates DNA fragments by size, the desired DNA band can be cut out of the gel and the DNA eluted (extracted) using techniques such as gel extraction kits, electroelution, or freeze-squeeze methods. This purified DNA fragment can then be ligated into a suitable vector (plasmid, bacteriophage, cosmid, etc.) using DNA ligase to construct recombinant DNA. This process is fundamental to recombinant DNA technology. Statement I is correct.Statement II Analysis: In agarose gel electrophoresis, DNA is negatively charged (due to phosphate groups in its backbone). When an electric field is applied, DNA migrates from the negative electrode (cathode/wells) towards the positive electrode (anode). Since the agarose gel acts as a molecular sieve, smaller DNA fragments experience less resistance and migrate faster (travel further from the wells). Larger fragments move slower and remain closer to the wells. Therefore, smaller fragments are found near the anode and larger fragments near the wells. Statement II is correct.Extended Explanation:Agarose gel electrophoresis is a key technique used to: (1) Separate DNA fragments by size; (2) Estimate the size of DNA fragments by comparison with a DNA ladder (molecular weight marker); (3) Verify restriction digestion patterns. The gel is stained with ethidium bromide (EtBr) or SYBR Green, which intercalates between DNA bases and fluoresces under UV light, making bands visible. The migration distance is inversely proportional to the log of the molecular weight of the DNA fragment. The process of isolating a specific band from the gel is called elution, and the resulting DNA can be used directly in cloning reactions to build recombinant DNA molecules.Key Concepts: Gel electrophoresis, DNA fragment separation, elution, recombinant DNA technology, anode vs cathode migration.

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