부산대학교 도서관

Q banded chromosome polymorphisms have been shown to segregate in a Mendelian manner in humans and may be used to determine the origin of marker chromosomes. Recent studies of Q polymorphisms on 2 patients, both mosaic for a supernumerary marker chromosome, and their families, yielded information regarding the origin of the marker. Patient: J.C., presented with classic features of Cat-Eye Syndrome: anal stenosis, fundal coloboma and preauricular tags and pits. The marker chromosome found was dicentric, as revealed by C banding, and the size of a G group chromosome. Comparison of Q banded karyotypes of the patient and her parents showed her to be 46XX/47XX, t(13;22) (13pter→13q11::22pter→22qll). E.S., a male evaluated for severe psychomotor retardation, cleft palate and congenital heart disease was found to be mosaic for a small bisatellited, metacentric chromosome. Comparison of polymorphisms of parents and child eliminated chromosomes 14, 15 & 22 from contributing to the origin of the marker. It is interpreted as arising post-zygotically from breaks in both number 13 chromosomes with subsequent reunion of the 2 short arms and satellite fragments such that the karyotype is 46XY/47XY, t(13;?13) (13pter→13q11::?13pte→?13q11). The data obtained from such studies is of importance in 1) determination of the frequencies of involvement of acrocentric chromosomes in such rearrangements, 2) defining phenotypic patterns associated with supernumerary markers and 3) facilitating accurate prenatal counseling when such a marker is detected in amniotic fluid cell cultures.