1. Of these, Trisomy 21 and Trisomy 18 are the most common. 2. A well-known example of trisomy is trisomy 21 or Down syndrome. 3. Lejeune's colleague, Marthe Gautier, disputes his claim as the first discoverer of trisomy 21 . 4. The term " trisomy 21 " is also used frequently. 5. However, the progeny of this carrier may inherit an unbalanced trisomy 21 , causing Down syndrome. 6. Some cases have been reported of people with Down syndrome having children with trisomy 21 . 7. One recent study showed that 77 % of Parisian fetuses diagnosed with trisomy 21 were aborted. 8. Medical literature reports four tetra-X pregnancies, two healthy, one with trisomy 21 , one stillborn with omphalocele. 9. The frequency of Trisomy 21 has been determined to be a function of Advanced maternal age. 10. The child displays classic dysmorphic features found in genetic mutations such as trisomy 21 , commonly known as Down's syndrome.
