Small supernumerary marker chromosomes (sSMCs) are extra chromosomes that are smaller than the standard chromosomes and can be found in various forms within an individual's genetic makeup.

All individuals were genotyped for 23 highly polymorphic markers. Positive evidence for linkage was found for a 10-cM region on the long arm of chromosome 20q13.1 q13.2 between markers D20S119 and ...