Ans.
In a cell, nucleus can be seen by a simple compound microscope, while DNA molecules cannot be seen under a compound microscope. This is because, DNA molecules are too small and these molecules are dispersed in nucleus in less compact state.
During DNA extraction, DNA is removed and purified from the cells by cell lysis. The extracted DNA is precipitated by ethanol that makes DNA molecules to clump together, makes it more condensed and DNA molecules become visible.