1. Homologous units of approximately 110 to 120 amino acids each which comprise the light and heavy chains of the immunoglobulin molecule and which serve specific functions. The light chain has two domains's, one in the variable region and one in the constant region of the chain; the heavy chain has four to five domains's, depending upon the class of immunoglobulin, one in the variable region and the remaining ones in the constant region.

2. A region of a protein having some distinctive physical feature or role.

Origin: Fr. Domaine, fr. L. Dominium, property, dominion

(05 Mar 2000)