Robertsonian translocation Down syndrome https://github.com/monarch-initiative/mondo/issues/5109 Chromosomal disorder in which (part or full) chromosome 21 is attached to another chromosome, resulting in the presence of a third copy of part of full chromosome 21 genetic material. A Robertsonian translocation is a structural chromosomal anomaly in which two acrocentric chromosomes break, resulting in the fusion of the nonhomologous chromosomes’ long arms to form a single, large chromosome. MONDO:0700082 UMLS:C5707615 GARD:0026350 NCIT:C188150 MEDGEN:1816520 translocation Down syndrome