Down's syndrome with a recombinant tandem duplication of chromosome 21 derived from a maternal ring.
An account is given of the cytogenetic investigations of a girl with Down's syndrome found to have a dicentric duplication of chromosome 21. This tandem type of rearrangement was interpreted as a recombinant derived from a single meiotic crossover between a maternal ring 21 and its normal homologue. A population of cells was also found in which breakage of the dicentric resulted in a chromosome 21 with a small terminal deletion. The mother and the proband's younger brother, who was also a ring 21 heterozygote, were both clinically normal.
D000328:Adult; D000649:Amniocentesis; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D002904:Chromosomes, Human, 21-22 and Y; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007621:Karyotyping; D008297:Male; D008540:Meiosis; D011247:Pregnancy; D011995:Recombination, Genetic; D012303:Ring Chromosomes