The negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Nucleosome
DNA is negatively charged because of its phosphate groups. Histones are proteins rich in the positively charged amino acids lysine and arginine. Eight histone molecules form a histone octamer. The DNA wraps around this octamer and forms the nucleosome, which is the repeating unit of chromatin. A typical nucleosome holds 200 bp of DNA.
(1) Nucleolus — Incorrect. The nucleolus is a round body inside the nucleus. Ribosomal RNA is made there.
(2) Nuclein — Incorrect. Nuclein is the name Friedrich Meischer gave in 1869 to the acidic substance he found in the nucleus. It was later called DNA.
(3) Nucleosome — Correct. It is the unit made of DNA wrapped around a histone octamer.
(4) Gene — Incorrect. A gene is a stretch of DNA that is the unit of inheritance. It is not a DNA-histone structure.
Note: A similar question was also asked in CUET (UG) 2026 on 06-06-2026 (Slot 1), and in CUET (UG) 2025 on 23-05-2025 (Slot 2).
NCERT Extract:
Packaging of DNA Helix – …
