The negatively charged DNA is wrapped around the positively charged histone octamer and forms a structure, called:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Nucleosome
Option (1) Chromosome — Incorrect. A chromosome is the whole thread of chromatin, coiled and condensed, that is seen during cell division. It is built from a very large number of nucleosomes packed further with the help of other proteins. It is not the small unit formed around one histone octamer.
Option (2) Nucleosome — Correct. The nucleosome is the unit of DNA wound around one histone octamer. Nucleosomes are the repeating unit of chromatin; under the electron microscope they look like ‘beads-on-string’.
Option (3) Centrosome — Incorrect. The centrosome is an organelle near the nucleus that holds two centrioles. In animal cells it helps to form the spindle during cell division. It has no DNA wrapped around histones.
Option (4) Peroxisome — Incorrect. A peroxisome is a small membrane-bound organelle of the cytoplasm. Its enzymes break down harmful hydrogen peroxide. It has nothing to do with packing DNA.
Note: A similar question was also asked in CUET (UG) 2026 on 06-06-2026 (Slot 1) and on 19-05-2026 (Slot 2).
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. Histones are organised to form a unit of eight molecules called histone octamer. The negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called nucleosome (Figure 5.4 a). A typical nucleosome contains 200 bp of DNA helix.”
