Question

Pick the incorrect statements among the following:
(i) A typical nucleosome contains 400 bp of DNA.
(ii) The positively charged DNA is wrapped around the negatively charged histone octamer to form a structure called nucleosome.
(iii) Histones are rich in the basic amino acid residues like asparagine and valine.
(iv) The packing of chromatin at higher level requires an additional set of proteins that collectively are referred to as non-histone chromosomal proteins.

• A. (i), (ii) and (iii)
• B. (ii), (iii) and (iv)
• C. (ii) and (iii)
• D. (i), (iii) and (iv)

Answer 1

The correct option is A (i), (ii) and (iii)

DNA is negatively charged due to the presence of phosphate groups in its nucleotides. This negatively charged DNA wraps around the positively charged histone proteins to form a nucleosome. A typical nucleosome has 200 bp of DNA.

Histones are rich in basic amino acids like lysine and arginine which carry positive charge in their side chains due to which they are positively charged.

Apart from histone proteins, the packing of chromatin at higher levels requires an additional set of proteins that collectively are referred to as non-histone chromosomal proteins (NHCs).