Arrange the steps of isolation of DNA from the source cell :
( I) Precipitation of DNA with chilled ethanol.
(II) Treatment of DNA strands with protease and RNase.
(III) Treatment of DNA strands with restriction endonuclease.
(IV) Isolation of DNA from bacterial cells by the treat ment of lysozyme.

Options

A. (IV), (I), (II), (III)
B. (II), (I), (IV), (III)
C. (IV), (I), (III), (II)
D. (IV), (II), (I), (III)

Answer

To arrange the steps of isolation of DNA from the source cell, we need to follow a logical sequence based on the biological processes involved. Here’s the step-by-step solution:

### Step-by-Step Solution:

1. **Isolation of DNA from bacterial cells by the treatment of lysozyme (IV)**:
- The first step in isolating DNA is to break open the bacterial cells. This is done using lysozyme, which specifically targets and breaks down the peptidoglycan layer of the bacterial cell wall, leading to cell lysis.

2. **Treatment of DNA strands with protease and RNase (II)**:
- After lysing the cells, the next step is to remove proteins and RNA that are associated with the DNA. This is achieved by treating the mixture with protease (to digest proteins) and RNase (to digest RNA), ensuring that only DNA remains.

3. **Precipitation of DNA with chilled ethanol (I)**:
- Once the DNA is free from proteins and RNA, it can be precipitated out of the solution. This is typically done by adding chilled ethanol, which causes the DNA to aggregate and become visible as a precipitate.

4. **Treatment of DNA strands with restriction endonuclease (III)**:
- Finally, if specific DNA fragments are needed, the precipitated DNA can be treated with restriction endonucleases. These enzymes cut the DNA at specific sequences, allowing for the isolation of desired fragments.

### Final Order of Steps:
- IV → II → I → III