In a standard DNA extraction protocol, why is detergent (e.g., SDS) added to the sample?

• A. To disrupt cell and nuclear membranes by solubilizing lipids and denaturing membrane proteins, releasing DNA into solution
• B. To amplify the DNA by serving as a primer for DNA polymerase
• C. To precipitate DNA out of solution by reducing its solubility in water
• D. To specifically cut DNA at restriction sites to generate fragments for analysis

Answer: (A)

Verified step by step guidance

1. Understand the role of detergent in the context of DNA extraction. Detergents like SDS (sodium dodecyl sulfate) are amphipathic molecules that interact with lipid bilayers.
2. Recognize that cell and nuclear membranes are primarily composed of lipid bilayers and proteins, which form barriers enclosing the DNA inside cells.
3. Know that the detergent disrupts these membranes by solubilizing the lipids and denaturing membrane proteins, effectively breaking down the structural integrity of the membranes.
4. This disruption releases the DNA from inside the nucleus and cytoplasm into the solution, making it accessible for further processing.
5. Differentiate this function from other options: detergents do not amplify DNA, precipitate DNA, or cut DNA at restriction sites; these are roles of other molecules or enzymes.