Biology Reference
In-Depth Information
FIGURE 5.6. Translocation between chromosomes 14 and 21. (A) The patient at three
years of age (From Meschede et al. 1998, Submicroscopic deletion in 14q32.3 through
a
de novo
tandem translocation between 14q and 21p, American Journal of Medical
Genetics 80:443-7, Copyright 1998 John Wiley & Sons, Inc. Reprinted by permission
of Wiley-Liss, Inc., a subsidiary of John Wiley & Sons, Inc.). Notice the posteriorly
rotated, low-set ears and the need for a hearing aide. (B) Ideograms representing the
patient's translocation. Arrows indicate the chromosomal breakpoints. The child has
one normal chromosome 14 (left), one normal 21 (middle), and one translocated
chromosome, t(14;21) (right), which results in monosomy for the distal portion of 14q.
Terminal deletions, as well as many interstitial deletions, have been
described (Therman and Susman 1993). Some deletions, such as those at
15q11-q13 or 22q11, associated with the Prader-Willi/Angelman syndromes
or DiGeorge/velocardiofacial syndromes, respectively, are relatively
common. Others, such as 5p- (cri-du-chat syndrome) or 4p- (Wolf-
Hirschorn syndrome), are rarely seen.
Many deletions or smaller microdeletions have been observed often
enough to be categorized into known clinical syndromes, i.e., similar dele-
tions producing similar phenotypic patterns. The following sections will
