Umbhalo Waphansi

a I-trisomy 21 isifo ozalwa naso esibangela ukukhubazeka engqondweni. Ngokuvamile ama-chromosome ahamba ngamabili, kodwa izingane ezizalwa zine-trisomy ziba nenkinga yokuba ne-chromosome eyengeziwe kwelinye ibhangqa. I-trisomy 21 ithinta i-chromosome 21.