Which laboratory method is most useful to separate genomic DNA fragments by size?

Titration is a quantitative chemical analysis method used to determine the concentration of a solute in a solution. It involves the gradual addition of a titrant to a solution until a reaction endpoint is reached, but it does not provide a means to separate DNA fragments by size. Therefore, it is not suitable for this purpose.

Spectrophotometry measures the amount of light absorbed by a sample at specific wavelengths to quantify the concentration of nucleic acids or proteins. While it can be used to assess DNA quantity and purity, it does not separate DNA fragments based on size, making it ineffective for this particular requirement.

Filtration is a physical separation method that utilizes a barrier to separate particles from a fluid based on size. However, it is not typically used for separating genomic DNA fragments, as it does not provide the resolution needed to distinguish between different sizes of DNA fragments effectively.