Natural Selection

A process in nature by which the organisms best suited to their environment are the ones most likely to survive and leave descendants.

Neutrality Theory

A recent theory proposing that at the level of DNA and protein sequence many changes are adaptively neutral and have little or no effect on the molecule's function.

Nucleic Acid

A complex molecule found in all cells. The two types of nucleic acids are DNA and RNA.

Nucleolus

A round body that forms in certain regions of specific chromosomes. They help in the formation of ribosomes, the cell's centers of protein production.

Nucleus

The structure in a cell that contains the chromosomes.