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Ch.26 Nucleic Acids and Protein Synthesis
Chapter 26, Problem 26.1

Is a DNA molecule neutral, negatively charged, or positively charged? Explain.

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DNA molecules are composed of nucleotides, each of which contains a phosphate group, a sugar, and a nitrogenous base.
The phosphate group in each nucleotide carries a negative charge due to the presence of negatively charged oxygen atoms.
As a result, the overall charge of a DNA molecule is negative because it contains many phosphate groups along its backbone.
The negative charge of DNA is important for its interactions with proteins and other molecules, as well as for its solubility in water.
In summary, a DNA molecule is negatively charged due to the presence of phosphate groups in its structure.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

DNA Structure

DNA, or deoxyribonucleic acid, is a molecule composed of two strands that coil around each other to form a double helix. Each strand is made up of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base. The phosphate groups in the backbone of the DNA contribute to its overall charge.
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Charge of DNA

DNA molecules are negatively charged due to the presence of phosphate groups in their structure. Each phosphate group carries a negative charge, which results in the overall negative charge of the DNA molecule. This charge plays a crucial role in the interactions of DNA with proteins and other molecules in the cell.
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Biological Implications of Charge

The negative charge of DNA is significant for its biological functions, including its interaction with positively charged proteins, such as histones, which help package DNA into chromatin. This charge also influences the behavior of DNA during processes like electrophoresis, where DNA fragments are separated based on size and charge.
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