Nucleosome Structure & DNA-Histone Wrapping — NEET Biology
✅ Asked in NEET 2026In 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. A typical nucleosome contains 200 bp of DNA helix. Nucleosomes constitute the repeating unit of a structure in nucleus called chromatin, thread-like stained (coloured) bodies seen in nucleus. The nucleosomes in chromatin are seen as 'beads-on-string' structure when viewed under electron microscope (EM).
NTA tests whether students understand that DNA wraps around a histone octamer (8 histone proteins) to form the nucleosome, the basic repeating unit of chromatin. Students often confuse the number of histone proteins (8, not 4 or 2) or forget that histones are positively charged (rich in lysine and arginine) which allows them to bind negatively charged DNA. The key is remembering: histone octamer + 200 bp DNA = nucleosome = "beads-on-string" pattern under electron microscope. Since this concept appeared 5 times in recent NEET exams, questions typically ask about histone composition, DNA wrapping, or the structure's appearance under EM.
This paragraph was tested 5 times in NEET.
Which statements are correct about packaging of DNA helix? A. Histones form octamer. B. Histones are negatively charged. C. Histones are rich in lysine and arginine. D. Positively charged DNA is wrapped around histone octamer. E. Higher-level chromatin packaging needs non-histone chromosomal proteins.
The nucleosome is the basic unit of DNA packaging in eukaryotes. It consists of a segment of DNA wound around which of the following? (NEET 2025)
Match List-I with List-II: (NEET 2024) List-I: A. Histone octamer B. Nucleosome C. Euchromatin D. Heterochromatin List-II: I. Loosely packed chromatin II. Densely packed chromatin III. Positively charged basic proteins IV. DNA wrapped around histone octamer Choose the correct answer from the options given below:
Read the following statements and choose the set of correct statements: (NEET 2022) (A) Euchromatin is loosely packed chromatin (B) Heterochromatin is transcriptionally active (C) Histone octamer is wrapped by negatively charged DNA in nucleosome (D) Histones are rich in lysine and arginine (E) A typical nucleosome contains 400 bp of DNA helix Choose the correct set:
Which of the following about histones is wrong? (NEET 2021)
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.