What groups are found on the exterior of the DNA double...

Name: Problem 25, Chapter 26: Fundamentals of General, Organic, and Biological Chemistry
Uploaded: 2022-01-16T16:45:27-08:00
Duration: 1 min 39 s
Channel: Ramesh Singh
Description: What groups are found on the exterior of the DNA double helix? In the nucleus, DNA strands are wrapped around proteins called histones. Would you expect histones to be neutral, positively charged, or negatively charged? Based on your answer, which amino acids do you expect to be abundant in histones and why?

What groups are found on the exterior of the DNA double helix? In the nucleus, DNA strands are wrapped around proteins called histones. Would you expect histones to be neutral, positively charged, or negatively charged? Based on your answer, which amino acids do you expect to be abundant in histones and why?

Key Concepts

Histone Positive Charge and Electrostatic Interactions

Histones are proteins that interact closely with DNA within the nucleus, and their function is largely dependent on electrostatic interactions. Because DNA is negatively charged due to the phosphate groups, histones must carry a positive charge to effectively bind and pack the DNA. This positive charge facilitates the neutralization of DNA's negative charge, enabling the formation of nucleosomes and the condensation of DNA into chromatin.

DNA Backbone and Negative Charge

DNA has a sugar-phosphate backbone where the phosphate groups are exposed on the exterior. These phosphate groups carry negative charges due to their ionized oxygen atoms, which contribute to the overall negative charge of the DNA molecule. This negative charge plays a critical role in the molecular interactions between DNA and other biomolecules.

Abundance of Basic Amino Acids

Basic amino acids such as lysine and arginine are typically abundant in histones because these residues are positively charged at physiological pH. Their side chains, containing amine groups, naturally repel negative charges, making them ideally suited to binding to the negatively charged phosphate groups of DNA. This abundance of basic residues is essential for the stability of the DNA-histone interaction and the proper organization of chromatin.

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