Final answer:
In gel electrophoresis, molecules move at different rates based on their charge-to-mass ratio. Larger or less compact molecules travel more slowly through the gel matrix, affecting how far they migrate in the gel. Supercoiled DNA migrates faster than linear DNA due to decreased friction in the gel.
The correct answer is option A charge-to-mass ratio.
Step-by-step explanation:
In gel electrophoresis, different molecules move at different rates based on their charge-to-mass ratio. This separation technique relies on the charged nature of the molecules, which in the case of nucleic acids like DNA and RNA, are negatively charged due to their phosphate backbones. When an electric field is applied, these negatively charged molecules are attracted towards the positive electrode. However, their movement through the gel matrix is impeded to different extents depending on their size and shape.
Larger molecules or those with higher molecular weight will travel less far than smaller molecules. Additionally, DNA conformation affects migration, as supercoiled DNA (more compact) migrates faster than linear DNA (more elongated). Agarose or polyacrylamide are the two types of gels commonly used, and they act as a molecular sieve, creating a porous medium that separates molecules based on size and shape. By comparing the distance traveled by the unknown samples to the distances traveled by molecules of known sizes (standard samples), researchers can estimate the relative size of the DNA fragments within a sample.