Which sequence of steps correctly describes a standard DNA extraction protocol from cultured cells?

Which sequence of steps correctly describes a standard DNA extraction protocol from cultured cells?

• A. Centrifugation, sequencing, amplification, and storage.
• B. Lysis to break cells, removal of proteins and contaminants (precipitation or organic extraction), precipitation/purification, and resuspension.
• C. Lysis only, followed by immediate resuspension.
• D. Precipitation, lysis, resuspension, and purification.

Answer: (B)

The main idea is that DNA extraction from cultured cells follows a logical sequence: release the DNA by breaking open the cells, remove proteins and other contaminants, purify or concentrate the DNA, and finally resuspend it for use. Starting with lysis to break the cells makes sense because DNA is inside the cells and needs to be freed. After lysis, removing proteins and other contaminants is essential to separate DNA from the rest of the cellular material; this is commonly done by precipitation or organic extraction, which helps remove proteins, lipids, and other impurities. Next comes precipitation or another purification step to concentrate and further clean the DNA. The final step is resuspending the purified DNA in an appropriate buffer or solution so it can be stored or used in subsequent experiments. Why the other sequences don’t fit: procedures like sequencing or amplification aren’t part of the extraction process themselves. A sequence that includes only lysis without purification misses the cleanup that’s crucial to obtain pure DNA. A sequence that starts with precipitation before lysis or omits the purification step would not effectively isolate DNA from the rest of the cellular material.

The main idea is that DNA extraction from cultured cells follows a logical sequence: release the DNA by breaking open the cells, remove proteins and other contaminants, purify or concentrate the DNA, and finally resuspend it for use.

Starting with lysis to break the cells makes sense because DNA is inside the cells and needs to be freed. After lysis, removing proteins and other contaminants is essential to separate DNA from the rest of the cellular material; this is commonly done by precipitation or organic extraction, which helps remove proteins, lipids, and other impurities. Next comes precipitation or another purification step to concentrate and further clean the DNA. The final step is resuspending the purified DNA in an appropriate buffer or solution so it can be stored or used in subsequent experiments.

Why the other sequences don’t fit: procedures like sequencing or amplification aren’t part of the extraction process themselves. A sequence that includes only lysis without purification misses the cleanup that’s crucial to obtain pure DNA. A sequence that starts with precipitation before lysis or omits the purification step would not effectively isolate DNA from the rest of the cellular material.