Answer:
i. Their size and charge
ii. This is due to the fact that they move when an electric current is applied.
Step-by-step explanation:
i. The components of DNA are of particular use in gel electrophoresis are their size and charge.
ii. This is because since the charge to mass ratio is constant for the DNA molecules, electrophoresis separates the molecules based on their sizes only. This is determined by the distance the DNA molecule moves in the gel. The smaller molecules move a large distance while the larger molecules move a small distance. This can thus be used to identify the molecules.