The definitions used in this glossary of terminology either have been provided by the authors of the articles, or have been extracted wholly or in part, or paraphrased from the following sources: The American Medical Association Encyclopedia of Medicine, Charles B. Clayman, MD, Medical Editor, Random House, New York, 1989; Biotechnology from A to Z, 2d Edition, William Bains, Oxford University Press, New York, New York, 2002; A Dictionary of Genetics, 6th Edition, Robert C. King and William D. Stansfield, Oxford University Press, New York, New York, 2002; Dorland's Illustrated Medical Dictionary, 29th and 30th Editions, W. B. Saunders Company, Philadelphia, 2000, 2003; Genes VII, Benjamin Lewin, Oxford University Press, New York, New York, 2000; The Gale Encyclopedia of Genetic Disorders, Volumes I and II, Stacey L. Blachford, Ed., Thomson Learning, New York, New York, 2002; The Merriam-Webster Dictionary, Merriam-Webster, Inc., Springfield, Massachusetts, 1997; Molecular Biology of the Cell, 3rd Edition, Bruce Alberts, et al., Garland Publishing, 1994; The Random House Dictionary of the English Language, Unabridged Edition, 1966; Webster's Ninth New Collegiate Dictionary, 1991.

DEFINITION:

heavy chains

Any of the larger polypeptide chains of antibody molecules, two identical heavy chains occurring (with two identical light chains) in each immunoglobulin monomer. The heavy chains determine the immunoglobulin class and subclass and are designated accordingly: y, a, µ, E, and d, the IgG, IgA, IgM, IgE, and IgD. The subclass may be designated by a number, e.g., y1, the heavy chain of IgG1. Heavy chains have four homology regions of about 110 amino acid residues: one variable region (V_H) and three constant regions (C_H1, C_H2, C_H3) except for µ and E chains which have an extra constant region (C_H4). See also immunoglobulin .