What can be said about the electric charge of DNA during gel electrophoresis?

During gel electrophoresis, DNA is known to carry a negative charge primarily due to its phosphate groups. Each nucleotide in the DNA backbone contains a phosphate group, which has a negatively charged phosphate ion. As DNA strands are subjected to an electric field during electrophoresis, they migrate toward the positive electrode because opposite charges attract. This behavior is fundamental to the separation of DNA fragments based on size, allowing smaller fragments to move more quickly through the gel matrix compared to larger ones.

The presence of positively charged proteins does not influence the overall charge of the DNA itself; rather, they may have their roles when associating with DNA during cellular processes. The idea that DNA is neutral is inaccurate, as it underlines the essential characteristic that enables DNA to be effectively separated during the electrophoresis technique. This is why the assertion that DNA is negatively charged due to its phosphate groups is correct and crucial for understanding its behavior in electrophoresis.