which type of mutation causes down syndrome?
Down Syndrome Mutation. Down Syndrome is caused by a trisomy. Another name for down syndrome is Trisomy 21. When a child receives its chromosomes pairs from their parents and a trisomy occurs...you receive 3 chromosomes instead of the two that are normally in a pair. When this happens on the 21st chromosome, it will most likely result in down syndrome. The mutation is a trisomy.