Historically, chloroform was used as part of a phenol-chloroform extraction method. Here's how it worked:

* Cell lysis: The first step involved breaking open the cells to release the DNA.

* Phenol: Phenol was then added to the mixture. Phenol is a strong denaturant that separates proteins from the DNA.

* Chloroform: Chloroform was added to create a biphasic system, meaning two layers formed. The top layer contained the aqueous solution with the DNA, while the bottom layer contained the phenol and denatured proteins.

Why chloroform is no longer used:

* Safety: Chloroform is a toxic and carcinogenic compound, posing a significant risk to researchers.

* Efficiency: Modern methods like spin columns or magnetic bead-based extraction are much faster, easier, and safer than phenol-chloroform methods. These techniques rely on different principles to isolate DNA.

Instead of chloroform, modern DNA extraction uses:

* Buffers: Buffers are used to create the right pH and salt concentration to lyse cells and separate DNA from other cellular components.

* Enzymes: Enzymes like proteinase K are used to digest proteins, further separating DNA from other cellular components.

* Spin columns or magnetic beads: These materials bind to DNA, allowing for its isolation and purification from the rest of the sample.

In summary, while chloroform was once used in DNA extraction, it is no longer considered a safe or efficient method. Modern DNA extraction techniques utilize alternative methods to achieve the same results with greater safety and ease.