Question

DNA is negatively charged why?substrate.

Answer 1

Phosphate groups in the DNA backbone carry negatively-charged oxygen molecules giving the phosphate-sugar backbone of DNA an overall negative charge. ... The negatively charged DNA can be pulled toward the positive field of the gel.

Answer 2

In the case of DNA, its negatively charged backbone can be utilized to immobilize the biological polymer onto flat, smooth, charged substrates; predominantly via electrostatic interactions. The DNA double helix is composed of A-T and C-G base pairs which are attached to a negatively charged sugar-phosphate backbone.