What Are the Characteristics of Individuals with Down Syndrome?
Types of Down Syndrome
95% of cases are of this type. Each cell in the body has three copies of 21st chromosome. The third copy of the 21st chromosome is also an independent chromosome.
In this type, either part or all of the extra 21st chromosome is attached to another chromosome.
In this case, some of the cells in the body carry two copies of the 21st chromosome as they should, while some cells have an extra 21st chromosome.