The origin and behavior of two isodicentric bisatellited chromosomes

D. L. Van Dyke, L. Weiss, M. Logan, G. S. Pai

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Abstract

Karyotyping revealed three cell lines in a boy with mental retardation and few other abnormalities. Thirty cells exhibited a normal karyotype, and 54 had an extra acrocentric chromosome of E group size with satellites on the long and short arms. The remaining 20 cells each had, in addition to the first marker (M1), a second tiny bisatellited chromosome (M2). C-banding demonstrated that both markers were dicentric. G-,C-, and Q-banding and satellite association data were consistent with the markers having originated from chromosome 15 material. We propose that M1 was formed from a meiotic breakage and a chromatid fusion in the proximal long arms of an acrocentric pair. This would have produced a symmetrical isodicentric chromosome, plus one or two acentric fragments. M2 then could have resulted from a dicentric bridge-break-synthesis-reunion phenomenon. This model of abnormal meiotic exchange can be generalized to encompass the formation of other dicentric isochromosome cases of isochromosome X.

Original languageEnglish (US)
Pages (from-to)294-300
Number of pages7
JournalAmerican Journal of Human Genetics
Volume29
Issue number3
StatePublished - 1977
Externally publishedYes

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ASJC Scopus subject areas

  • Genetics

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Van Dyke, D. L., Weiss, L., Logan, M., & Pai, G. S. (1977). The origin and behavior of two isodicentric bisatellited chromosomes. American Journal of Human Genetics, 29(3), 294-300.