Molecular Biology

The process of DNA fingerprinting involves several sequential steps. Understanding the correct order is critical for accurate results. Below are the steps explained in the order they are performed:

1. Isolation of DNA: The initial step is to extract DNA from cellular material. This involves breaking open cells and using chemical procedures to purify the DNA, free from proteins and other contaminants.
2. Digestion of DNA by restriction endonuclease: Once isolated, the DNA is cut into fragments using restriction enzymes known as endonucleases. These enzymes recognize specific sequences and cleave the DNA at these sites, resulting in a mixture of smaller DNA fragments.
3. Transfer (blotting) of separated DNA fragments to synthetic membrane: The fragmented DNA is then separated based on size by gel electrophoresis. These fragments are transferred onto a synthetic membrane, a process called blotting, where they are immobilized.
4. Hybridisation using labelled VNTR probe: The membrane with immobilized DNA fragments is exposed to VNTR (Variable Number Tandem Repeats) probes that have been labelled. These probes hybridize to specific DNA sequences, and their patterns can be visualized using suitable detection methods.

This sequence is represented by option: (B), (A), (D), (C).

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

To solve the problem, we need to identify the enzyme that helps unwind the DNA strands during the process of DNA replication.

1. Understanding DNA Replication:

- DNA replication is the process by which a cell makes an exact copy of its DNA before cell division.
- The double-stranded DNA must be unwound so that each strand can serve as a template for the new strand.
- This unwinding requires special enzymes.

2. Role of the Enzyme:

- The enzyme responsible for unwinding or "unzipping" the double helix structure of DNA is called Helicase.
- Helicase breaks the hydrogen bonds between the two strands of DNA, separating them into single strands.
- This creates a replication fork where new DNA strands can be synthesized.

3. Other Enzymes in DNA Replication (for context):

• DNA Polymerase: Adds new nucleotides to the growing DNA strand.
• Primase: Synthesizes RNA primers needed to start replication.
• Ligase: Joins fragments of DNA together.

Final Answer:

The enzyme responsible for unwinding the DNA during replication is Helicase.