Robertsonian translocation Down syndrome
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.