chromosome 21
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:
- chromosome 21
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Chromosome 21 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 21 is the smallest human chromosome, spanning about 47 million base pairs (the building blocks of DNA) and representing approximately 1.5 percent of the total DNA in cells. Chromosome 21 likely contains between 200 and 400 genes. There are many conditions caused by changes in the structure or number of copies of chromosome 21, including several cancers, Down syndrome, mental retardation, etc. (NIH)
Used in 1 Term definition
Used in 1 Term definition