What is the difference between trisomy21 and trisomy18
The difference between trisomy 21 and trisomy 18 is the number of chromosomes involved. Trisomy 18 (Edward's syndrome) is caused by addition or deletion of an 18th chromosome whereas trisomy 21 is caused by presence of a 21st chromosome.
Trisomy 18 is typically fatal with many deformities. Trisomy 21 is downs syndrome.