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

To determine which statements are incorrect, let's analyze each one:

1. (A) "Fragments of DNA can be separated by ELISA." 
   Explanation: ELISA (Enzyme-Linked Immunosorbent Assay) is a technique primarily used to detect proteins and antigens, not to separate DNA fragments. Therefore, this statement is incorrect.
2. (B) "Transformation is a procedure through which a piece of DNA is introduced in a host bacterium." 
   Explanation: Transformation indeed refers to the method of introducing foreign DNA into a host cell, typically a bacterium. This statement is correct.
3. (C) "Recombinant DNA technology does not involve isolation of a desired DNA fragment." 
   Explanation: Recombinant DNA technology involves isolating the desired DNA fragment to be manipulated or studied. Hence, this statement is incorrect.
4. (D) "DNA ligases are used for stitching DNA fragments into a vector." 
   Explanation: DNA ligases are enzymes used to join DNA strands together by catalyzing the formation of phosphodiester bonds, which is essential in inserting DNA fragments into vectors. This statement is correct.

Based on the analysis, the incorrect statements are (A) and (C). The correct answer to the given question is thus: (A) and (C) only

Answer 2

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.