Nucleic Acids

Nucleotide

A molecule made up of a phosphate group and a nitrogenous base bonded to a 5-carbon sugar.

Nucleic acid

A molecule made up of nucleotides linked to form a chain or strand.

Phosphodiester bond

Covalent bonds between the phosphate group on the 5′ carbon of one nucleotide and the -OH group on the 3′ carbon of a second nucleotide.

Complementary base pairing

Hydrogen bonding between A-T or A-U and G-C pairs in a nucleic acid.

Primary structure

The sequence of nucleotides in a nucleic acid, read 5′ to 3′.

Secondary structure

Formation of a double helix in DNA or a stem-and-loop structure in RNA, based on complementary base pairing.

Sugar-phosphate backbone

The "spine" of 5-carbon sugars and phosphate groups in a nucleic acid (the nitrogenous bases project from this backbone).

Antiparallel strands

Strands of DNA or RNA that align in opposite 5′ to 3′ orientation.

Monomer

A small "subunit" molecule that can be linked to another, via a covalent bond, to form a larger molecule called a polymer.

Polymer

A large molecule made up of strings of covalently bonded small molecules (monomers).