Based on the provided sources and standard biological principles:

• Statement (a) is correct: Euchromatin is the region of chromatin that is loosely packed and stains lightly.
• Statement (b) is incorrect: Heterochromatin is densely packed and transcriptionally inactive, whereas euchromatin is transcriptionally active.
• Statement (c) is correct: Negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called a nucleosome .
• Statement (d) is correct: Histones are basic proteins that acquire a positive charge due to the abundance of basic amino acid residues, specifically lysine and arginine.
• Statement (e) is incorrect: A typical nucleosome contains approximately 200 base pairs (bp) of DNA helix, not 400 bp.