Small supernumerary marker chromosomes (sSMC) can be defined as structurally abnormal chromosomes that cannot be identified or characterized unambiguously by conventional banding cytogenetics alone, and are (in general) equal in size or smaller than chromosome 20 of the same metaphase spread (Liehr et al., 2004). sSMC are relatively uncommon in the general population. They have been detected wi...

sSMCs are a major clinical problem, especially when detected prenatally during cytogenetic analysis. The risk for an abnormal phenotype in prenatally ascertained de novo cases with sSMC is ~13%. This has been refined to 7% for sSMC from acrocentric autosomes (excluding 15s) compared with ∼28% for nonacrocentric autosomes [4] and 30% for all sSMC carriers [1]. Strikingly, 30-50% of pregnancies d...

Cytogenetic analyses were carried out in a populational sample of Iheringichthys labrosus from the Guaraúna River (Upper Tibagi River; Paraná State, Brazil) in order to provide a karyotypic comparison with another previously studied population from the Lower Tibagi River, characterized by the presence of 32m + 8sm + 6st + 10a (2n = 56, FN = 102) and occurrence of supernumerary chromosomes (80% ...

Small supernumerary marker chromosomes (sSMC) in human are defined as additional centric derivatives smaller than chromosome 20. In the majority of the cases only one sSMC is present, leading to a more or less stable karyotype of 47,XX,+mar or 47,XY,+mar. In approximately 1.4% of sSMC cases two or up to seven markers of different chromosomal origin are reported. According to the literature a sS...

In this study the substantial and in part contradictory data available in the literature was collected concerning the frequency of small supernumerary marker chromosomes (sSMC) in the human population in general, and in special subpopulations. One hundred and thirty-two studies on sSMC were reviewed. In summary 1,288,693 cytogenetically studied cases detecting 980 sSMC were compiled. In 132 int...