(N/A) Nucleic acid is the genetic material of all organisms without exception. In the majority of organisms,it is $DNA$.
To cut the $DNA$ with restriction enzymes,it needs to be in a pure form,free from other macromolecules.
Since $DNA$ is enclosed within membranes,we must break the cell open to release $DNA$ along with other macromolecules such as $RNA$,proteins,polysaccharides,and lipids.
This is achieved by treating the bacterial cells,plant,or animal tissue with specific enzymes: lysozyme for bacteria,cellulase for plant cells,and chitinase for fungus.
$RNA$ can be removed by treatment with ribonuclease,whereas proteins can be removed by treatment with protease.
Other molecules are removed by various treatments,and the purified $DNA$ ultimately precipitates out after the addition of chilled ethanol. This can be observed as a collection of fine threads in the suspension,which can be removed by spooling.