The basic nature of histone proteins allows them to tightly pack the DNA helix. This property is due to the presence of positive charges on which specific part of their constituent basic amino acid residues?

Step-by-step solution

Histone proteins are rich in basic amino acid residues, primarily lysine and arginine. These basic amino acids possess side chains (R groups) that carry a positive charge at physiological pH. The positive charges on the side chains of these amino acids interact strongly with the negatively charged phosphate groups of the DNA backbone, allowing histones to tightly pack the DNA helix into nucleosomes. Carboxyl groups are generally negatively charged, while peptide bonds and alpha-carbon atoms do not carry the positiv