Marker Chromosomes: Cytogenetic characterization and implications for prenatal diagnosis

Abstract

Satellited marker chromosomes were identified in four individuals from unrelated families; one was first encountered in cultured amniotic fluid cells obtained for prenatal diagnostic studies. We present cytogenetic characterization of these marker chromosomes and clinical findings in the individuals carrying them. Identification of a marker chromosome in amniotic fluid cell cultures presents problems in genetic counseling, as it is often difficult to determine the clinical significance of such a finding. Chromosome-banding techniques now allow the precise identification of satellited marker chromosomes originating from chromosome 15. Presence of a supernumerary bisatellited der(15) marker chromosome containing the proximal long arm of 15 has been associated with mental and developmental retardation. Application of chromosome-banding techniques was useful in characterization of the marker chromosomes and providing prenatal genetic counseling.

Marker chromosomes in A series of 10000 prenatal diagnoses. Cytogenetic and follow‐up studies

“…All familial markers were first seen in amniotic fluid cells. Prospective studies evaluating the consequence of a marker for the phenotype have not been carried out so far (Mohandas et al, 1985). These authors described a normal phenotype in association with a marker chromosome inv dup (1 5 ) in two out of 25 cases.…”

Molecular cytogenetic characterization of marker chromosomes found at prenatal diagnosis

“…De novo supernumerary marker chromosomes found at prenatal diagnosis can cause problems for genetic counselling since the resulting clinical findings may range from normal to severe mental retardation in association with congenital abnormalities (Benn and Hsu, 1984;Mohandas et al, 1985;Sachs et al, 1987;Kaffe and Hsu, 1988;Cheung et al, 1990;Warburton, 1991). The incidence of supernumerary marker chromosomes has been estimated in different studies to range between 0.4/ 1000 and 1.5/1000 (Sachs et al, 1987;Hook and Cross, 1987;Kaffe and Hsu, 1988;Djalali, 1990;Warburton, 1991).…”

Inv dup (15): Prenatal diagnosis and postnatal follow‐up

“…Detailed sonographic evaluations are not expected to be helpful, since the extra chromosome obviously does not cause major malformations. Normal results of autopsy, as in the fetuses reported by Mohandas et al (1985) as well as normal development in the first few months of life do not exclude the abnormalities associated with inv dup (1 5). Risk assessment seems only possible based on long-term follow-up of patients ascertained by chance.…”

“…Dealing with the clinical significance of supernumerary marker chromosomes, inv dup (1 5) has become a differential diagnosis of major practical concern, since special staining procedures like DA-DAPI (Schweitzer et al, 1978) have become available. When diagnosed prenatally, no phenotypic effects have been observed so far (Stetten et al, 1981 ;Mohandas et al, 1985;Wisniewski and Doherty, 1985). A newborn with inv dup (1 5) detected in a screening programme was normal (Buckton et al, 1980).…”