This is called trisomy 21. In mosaic Down syndrome, some of the person’s cells have three copies of chromosome 21, but some cells have two copies of this chromosome, resulting in a mixture.

Once Zambelli was tested, it came back positive for mosaic Down syndrome, or trisomy 21 mosaicism/mosaic trisomy 21. According to the Stanford Children's Hospital, this form of Down syndrome is ...

21 in a child with some mongoloid features, who was of normal intelligence. Chromosome analysis revealed her to be a mosaic with a mixture of cells carrying a normal chromosome complement and ...

A century after Down syndrome was first described, scientists discovered that the root cause of this disorder is a condition called trisomy 21. What strides in research have been made since then?

Could two pieces of a stone mosaic ever be identical? Of course, the answer is no--and each stone’s variation subtly contributes value to the finished work. Why should your cells be any different?