What is the structure of the DNA molecule and chromosomes?

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paigejeanes eNotes educator| Certified Educator

The structure of the DNA molecule is called a double helix made up of nucleotides.  Nucleotides are made of three parts: deoxyribose (sugar), phosphate, and nitrogenous bases.  The double helix of DNA looks like a spiraling ladder.  The rungs of this ladder are made up of nitrogenous bases and the sides of the ladder are made of deoxyribose and phosphate. Their are four nitrogenous bases that make up a DNA molecule; they are thymine, adenine, guanine and cytosine.  Adenine always pairs with thymine and guanine always pairs with cytosine.  These nitrogenous bases are held together using hydrogen bonds.

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