Amniocentesis Research Today is a free monthly online journal that collates and summarizes the latest research about Amniocentesis, including details on pregnancy, prenatal screening, diagnosis, risks, down syndrome.

Y chromosome heterochromatin of differing lengths in two cell populations of the same individual.

Akkari Y, Lawce H, Kelson S, Smith C, Davis C, Boyd L, Magenis RE, Olson S

Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon.

OBJECTIVE: To present a prenatal diagnosis report on a case where G-banding analysis of fetal metaphase chromosomes showed populations of cells with two different Y chromosomes; one with a short block of heterochromatin (Yqh-) and one with a longer block of heterochromatin (Yqh+). METHODS: These two populations of the Y chromosome were studied using fluorescent quinacrine banding and fluorescent in situ hybridization (FISH). A chromosome paint corresponding to the euchromatic region of the Y chromosome, and probes corresponding to the SRY, DYZ1, and DYZ3 regions were used for this study. RESULTS: Both Y chromosomes appeared to be structurally normal by these analyses. Subsequent ultrasound examination at 20 weeks' gestation revealed normal male genitalia. Follow-up with a neonatal blood sample analysis confirmed the above findings. CONCLUSIONS: This study reports a direct prenatal diagnosis case of two populations of the Y chromosome in the same individual. This apparent mosaicism may be explained by a postzygotic simple deletion or unequal crossover event between sister chromatids in the DYZ region.

Published 2 May 2005 in Prenat Diagn, 25(4): 304-6.
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