AP Biology Module 5 Vocabulary

Nitrogenous base

A nitrogen-containing compound that makes up part of a nucleotide

Purine

In nucleic acids, either of the bases adenine and guanine, which have a double-ring structure

Adenine

A purine base (A)

Guanine

A purine base (G)

Pyrimidine

In nucleic acids, any of the bases thymine, cytosine, and uracil, which have a single-ring structure.

Thymine

A pyrimidine base (T)

Cytosine

A pyrimidine base (C)

Directionality/Polarity

An asymmetry such that one end of a structure differs from the other.

5' end

The end of a DNA or RNA molecule that has a free phosphate group. By convention, the end is considered the end with the first nucleotide.

3' end

The end of a DNA or RNA molecule that has a free __ hydroxyl group. By convention, the __ end is considered the end with the last nucleotide.

Double helix

The structure formed by two strands of complementary nucleotides that coil around each other.

Antiparallel

Oriented in opposite directions, like the two strands in a DNA molecule.

Complementary

Describes the relationship of purine and pyrimidine bases, in which the base A pairs only with T, and G pairs only with C.

Uracil (U)

A pyrimidine base in RNA, where it replaces thymine found in DNA

Central dogma

The idea that information in a cell usually flows from DNA to RNA to protein.