NEET 2023 Zoology Recombinant DNA Technology MCQ Question

To understand the correct sequence in the formation of Recombinant DNA, let’s break down each of the steps involved in the process and clarify why option (4) B, C, D, A is indeed the correct answer, despite your indication that the answer should be D.

Steps in Recombinant DNA Technology

1. Cutting of DNA at specific location by restriction enzyme (Step B):

   • This is the first step where specific enzymes known as restriction endonucleases are used to cut the DNA at specific recognition sites. This allows for the isolation of the desired gene fragment from a larger DNA molecule.

2. Isolation of desired DNA fragment (Step C):

   • After cutting the DNA, the next logical step is to isolate the desired DNA fragment from the rest of the DNA. This can be done using various techniques such as gel electrophoresis or column purification.

3. Amplification of gene of interest using PCR (Step D):

   • Once the desired DNA fragment is isolated, the polymerase chain reaction (PCR) is used to amplify this fragment. This technique allows for the creation of millions of copies of the specific DNA segment, ensuring that there is enough material for insertion into a host.

4. Insertion of recombinant DNA into the host cell (Step A):

   • Finally, the amplified recombinant DNA is introduced into a suitable host cell. This is typically done using methods such as transformation, transfection, or electroporation, which enable the uptake of the DNA by the host organism.

Correct Sequence of Steps

Thus, the correct sequence of steps is:

• B (Cutting) → C (Isolation) → D (Amplification) → A (Insertion)

This leads us to the correct answer being option (4) B, C, D, A.

Why Other Options Are Incorrect

1. Option (1) C, A, B, D:

   • This sequence incorrectly starts with isolation (C) and then jumps to insertion (A) before cutting (B) and amplification (D). This is illogical as the DNA must first be cut before any isolation or amplification can take place.

2. Option (2) C, B, D, A:

   • This option also starts with isolation (C), which is incorrect because you must first cut the DNA (B) to obtain a fragment before isolating it.

3. Option (3) B, D, A, C:

   • This option suggests cutting the DNA (B), then amplifying it (D), and inserting it (A) before isolation (C). However, the DNA fragment must be isolated before amplification can occur, making this sequence incorrect.

Conclusion

Therefore, the step-by-step analysis clearly shows that the correct sequence of the steps in the formation of recombinant DNA is B, C, D, A, making option (4) the correct choice. This understanding is crucial for students preparing for exams like NEET/JEE, where clarity on processes such as recombinant DNA technology can greatly impact their performance.