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Structure of Nucleic Acids


Bases, Sugars, and Phosphates


Problem : What three structures compose a nucleotide?

A nucleotide is composed of a five-carbon sugar, nitrogen base, and one or more phosphate groups.

Problem : What is the name of the type of bond that occurs between a phosphate and ribose group? Between a ribose and nitrogen base group?

An ester bond forms between a phosphate group and a ribose group. A glycosidic bond forms between a ribose group and a nitrogen base group.

Problem : Name the bond that forms between nucleotide groups.

A phosphodiester bond forms between nucleotides to form nucleic acids.

Problem : Explain the significance of hydrogen bonds in DNA helices.

While hydrogen bonds do contribute a small amount to the stability of helices, their main contribution is to the specificity of a helix. Hydrogen bonds dictate the complementary base pairing that aligns anti-parallel nucleic acids strands in a DNA helix.

Problem : What does Chargaff's rule say?

Chargaff's rule states that the molar ratios of A to T and G to C bases are approximately equal in a DNA helix. This is a result of complementary base pairing between single strands of DNA in a helix. Each A pairs with a T and each G pairs with a C, making their molar ratios equal.