Which statement is true regarding agarose gel electrophoresis of PCR-SSP products?

The statement about DNA migrating toward the positive electrode is accurate due to the inherent properties of DNA molecules. DNA carries a negative charge because of its phosphate backbone. When an electric field is applied during agarose gel electrophoresis, the negatively charged DNA fragments are attracted to the positive electrode. This migration occurs through the gel matrix, allowing for the separation of DNA fragments based on size; smaller fragments can move more easily through the pores of the gel compared to larger fragments.

In contrast to the correct answer, other statements contain inaccuracies. For instance, short DNA fragments actually move faster than longer fragments in the gel because the smaller size enables them to navigate through the agarose matrix more easily. Ethidium bromide staining provides a uniform intensity of fluorescence based on the amount of DNA present, meaning smaller fragments do not appear inherently brighter than larger ones; their brightness correlates with quantity rather than size. Moreover, the assertion that differences in molecular weight less than 100 base pairs cannot be resolved is misleading, as agarose gel electrophoresis can effectively separate DNA fragments with smaller size differences, depending on the percentage of agarose used in the gel.