Robinson W P, Binkert F, Bernasconi F, Lorda-Sanchez I, Werder E A, Schinzel A A
Institut für Medizinische Genetik der Universität Zürich, Switzerland.
Am J Hum Genet. 1995 Feb;56(2):444-51.
Studies of uniparental disomy and origin of nonmosaic trisomies indicate that both gain and loss of a chromosome can occur after fertilization. It is therefore of interest to determine both the relative frequency with which gain or loss can contribute to chromosomal mosaicism and whether these frequencies are influenced by selective factors. Thirty-two mosaic cases were examined with molecular markers, to try to determine which was the primary and which was the secondary cell line: 16 cases of disomy/trisomy mosaicism (5 trisomy 8, 2 trisomy 13, 1 trisomy 18, 4 trisomy 21, and 4 involving the X chromosome), 14 cases of 45,X/46,XX, and 2 cases of 45,X/47,XXX. Of the 14 cases of mosaic 45,X/46,XX, chromosome loss from a normal disomic fertilization predominated, supporting the hypothesis that 45,X might be compatible with survival only when the 45,X cell line arises relatively late in development. Most cases of disomy/trisomy mosaicism involving chromosomes 13, 18, 21, and X were also frequently associated with somatic loss of one (or more) chromosome, in these cases from a trisomic fertilization. By contrast, four of the five trisomy 8 cases were consistent with a somatic gain of a chromosome 8 during development from a normal zygote. It is possible that survival of trisomy 8 is also much more likely when the aneuploid cell line arises relatively late in development.
单亲二体性及非嵌合三体起源的研究表明，受精后染色体的增加和减少均可能发生。因此，确定增加或减少导致染色体嵌合的相对频率以及这些频率是否受选择因素影响是很有意义的。利用分子标记对32例嵌合病例进行了检查，以试图确定哪一个是主要细胞系，哪一个是次要细胞系：16例二体/三体嵌合（5例8号三体、2例13号三体、1例18号三体、4例21号三体以及4例涉及X染色体）、14例45,X/46,XX以及2例45,X/47,XXX。在14例45,X/46,XX嵌合病例中，正常二体受精导致的染色体丢失占主导，这支持了如下假说：只有当45,X细胞系在发育过程中相对较晚出现时，45,X才可能存活。大多数涉及13号、18号、21号染色体及X染色体的二体/三体嵌合病例也常伴有一条（或多条）染色体的体细胞丢失，在这些病例中是三体受精导致的。相比之下，5例8号三体病例中有4例与正常合子发育过程中8号染色体的体细胞增加相符。当非整倍体细胞系在发育过程中相对较晚出现时，8号三体存活的可能性也可能大得多。
