Question

Which of the following statements are incorrect?
(A) Fragments of DNA can be separated by ELISA.
(B) Transformation is a procedure through which a piece of DNA is introduced in a host bacterium.
(C) Recombinant DNA technology does not involve isolation of a desired DNA fragment.
(D) DNA ligases are used for stitching DNA fragments into a vector.
Choose the answer from the options given below:

• A. (A) and (C) only
• B. (A) and (B) only
• C. (B) and (C) only
• D. (A), (C) and (D) only

Answer 1

The Correct Option is A

Options (A) and (C) are Incorrect in DNA Analysis 

(A) DNA Fragments are Separated by Gel Electrophoresis, Not ELISA

Enzyme-Linked Immunosorbent Assay (ELISA) is a technique used for detecting and quantifying proteins, antibodies, and hormones, not for DNA separation.

Correct Technique: Gel Electrophoresis

The correct method for DNA fragment separation is gel electrophoresis, which works based on:

• Charge-based separation: DNA molecules are negatively charged due to phosphate groups.
• Size-dependent movement: Smaller DNA fragments migrate faster through the gel matrix.
• Use of agarose gel: Provides a medium for the DNA to travel when subjected to an electric field.

The movement of DNA fragments is described by the equation:

\( d \propto \frac{1}{\log M} \)

where:

• \( d \) = Distance traveled
• \( M \) = Molecular weight of the DNA fragment

Conclusion: Since ELISA does not separate DNA fragments, option (A) is incorrect.

(C) Recombinant DNA Technology Involves the Isolation of a Desired DNA Fragment

Recombinant DNA technology is a genetic engineering process that requires the precise isolation of a target DNA fragment before it can be inserted into a vector.

Steps in Recombinant DNA Technology:

1. Isolation of DNA: Extracting the desired gene from the donor organism.
2. Cutting DNA with Restriction Enzymes: Using molecular scissors to obtain the fragment.
3. Insertion into a Vector: Ligating the DNA into a plasmid.
4. Transformation: Introducing the recombinant DNA into a host cell.
5. Selection & Screening: Identifying transformed cells.

Conclusion: Since isolation is a fundamental step, option (C) is incorrect.

Final Summary

• (A) is incorrect because DNA fragments are separated by gel electrophoresis, not ELISA.
• (C) is incorrect because recombinant DNA technology requires the isolation of the desired DNA fragment as an essential step.