A t(21q21q) ring chromosome.
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D002904:Chromosomes, Human, 21-22 and Y; D003878:Dermatoglyphics; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D007621:Karyotyping; D008297:Male; D008938:Mitosis; D009030:Mosaicism; D013194:Staining and Labeling