ISSN:
1432-1203
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Ten new cases of accessory bisatellited marker chromosomes examined in different laboratories are reported. As a basis for genetic counselling in the context of prenatal diagnosis a cytogenetic categorization of such marker chromosomes is proposed and an estimation of the genetic risk associated with each category is carried out. The results are as follows: 1. There is no increased risk for offspring with abnormal phenotype born to a healthy carrier of an accessory bisatellited marker chromosome with either a single or two closely adjacent C-bands (Category AI or AII). 2. The unbiased sample of cases with de novo accessory bisatellited marker chromosomes of categories AI and AII is too small to allow a satisfactory estimation of the actual risk that, in case of such a prenatal finding, the foetus may not show a normal phenotype as a consequence of the marker chromosome. There is, however, evidence that this risk may be lower than 10%. 3. Accessory bisatellited marker chromosomes showing a discrete pattern of G- or R-bands situated between two distant C-bands (Category AIII) usually indicate a chromosomal imbalance giving rise to an abnormal phenotype. Mosaic carriers of such dicentric marker chromosomes may, however, present a normal phenotype.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00286654
Permalink