Histones are rich in amino acids -

The correct answer is Option (4) → Lysine and arginine

In eukaryotes, the long, negatively charged DNA is wound round proteins called histones. Opposite charges attract, so histones must be positively charged (basic) to hold the DNA.

Option (1) Lysine and leucine — Incorrect. Lysine is right, but leucine carries no charge in its side chain. It cannot help the histone bind DNA.

Option (2) Lysine and phenylalanine — Incorrect. Phenylalanine is also an uncharged amino acid. Only lysine of this pair is basic.

Option (3) Arginine and asparagine — Incorrect. Arginine is right, but asparagine is not a basic amino acid. Its side chain has no positive charge.

Option (4) Lysine and arginine — Correct. These are the two basic amino acids of the histones. Their positive charges bind the negative phosphate groups of DNA, and eight histone molecules with DNA wrapped round them form a nucleosome.

Note: A similar question was also asked in CUET (UG) 2026 on 25-05-2026 (Slot 1) and on 22-05-2026 (Slot 1).

NCERT Extract:
Packaging of DNA Helix – “… In eukaryotes, this organisation is much more complex. There is a set of positively charged, basic proteins called histones. A protein acquires charge depending upon the abundance of amino acids residues with charged side chains. Histones are rich in the basic amino acid residues lysine and arginine. Both the amino acid residues carry positive charges in their side chains.”