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Cytogenetics in Clinical Medicine

Janet D. Rowley, MD
JAMA. 1969;207(5):914-919. doi:10.1001/jama.1969.03150180044009.
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The purpose of this article is to provide basic information about (1) the techniques used to prepare human chromosomes, (2) the nomenclature used in identifying human chromosomes, and (3) the detection of chromosomal aberrations. Information currently accumulated about human chromosomal abnormalities has been reviewed elsewhere.1

Chromosomes are the units of organization of deoxyribonucleic acid which code for the genetic information present in the nucleus of the cell. In addition to DNA, chromosomes contain ribonucleic acid, histone (low molecular weight basic protein), and a more complex acidic residual protein. The manner in which these four macromolecules are bound together to form a chromosome is not yet fully understood. The DNA in the chromosomes undergoes exact replication before a cell divides. For most of the cell cycle, chromosomes are in an extended state and cannot be counted or identified. Early in cell division the chromosomes begin to contract so that by


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