Which of the following statements are correct with reference to packaging of DNA helix ? A. Histones are organized to form a unit of eight molecules called histone octamer. B. Histones are negatively charged basic proteins. C. Histones are rich in the basic amino acid residues - lysine and arginine. D. The positively charged DNA is wrapped around the histone octamer to form nucleosome. E. The packaging of chromatin at higher levels requires an additional set of proteins called non-histone chromosomal proteins. Choose the correct answer from the options given below :

Solution & Explanation

Answer: (A) A, C and E only. A, C and E are correct (histone octamer of eight molecules; histones rich in lysine and arginine; higher-level packaging needs NHC proteins). B is wrong because histones are POSITIVELY charged basic proteins, and D is wrong because the NEGATIVELY charged DNA (not positively charged) is wrapped around the histone octamer. NCERT Ch 5, p.83, lines 027-037: "There is a set of positively charged, basic proteins called histones... Histones are rich in the basic amino acid residues lysine and arginine... 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"; p.84, line 003: "Non-histone Chromosomal (NHC) proteins."