In eukaryotic chromosome structure, why do histones bind tightly to DNA?

• A. Histones bind tightly to DNA primarily through sequence-specific base-pair recognition in the major groove, similar to many transcription factors.
• B. Histones are rich in positively charged basic amino acids (e.g., lysine and arginine) that electrostatically attract the negatively charged phosphate backbone of DNA.
• C. Histones form covalent bonds with the sugar-phosphate backbone of DNA, permanently linking DNA to the nucleosome core.
• D. Histones bind tightly because they are negatively charged and therefore repel DNA into a compact structure.

Answer: (B)

Verified step by step guidance

1. Understand the chemical nature of DNA: DNA has a negatively charged backbone due to the phosphate groups in its sugar-phosphate backbone.
2. Recognize the composition of histones: Histones are proteins rich in positively charged basic amino acids such as lysine and arginine.
3. Apply the concept of electrostatic interactions: The positive charges on histones are attracted to the negative charges on the DNA backbone, leading to tight binding.
4. Note that this interaction is primarily electrostatic and not sequence-specific, meaning histones bind along the DNA regardless of the base sequence.
5. Conclude that this electrostatic attraction facilitates the packaging of DNA into nucleosomes, the fundamental units of chromatin structure.