The most common form of Down's syndrome, caused by an extra copy of chromosome number 21.
Example sentencesExamples
Trisomy 21 can be detected in the first few months of pregnancy by amniocentesis.
Microcephaly can also be caused by the chromosomal disorder, trisomy-21 Down syndrome, and by environmental factors, such as fetal alcohol syndrome and fetal exposure to radiation before 15 weeks gestation.
The majority (about 94%) of children with Down Syndrome are born with standard Trisomy 21, which is not hereditary.
Definition of trisomy-21 in US English:
trisomy-21
noun
Medicine
The most common form of Down syndrome, caused by an extra copy of chromosome number 21.
Example sentencesExamples
Microcephaly can also be caused by the chromosomal disorder, trisomy-21 Down syndrome, and by environmental factors, such as fetal alcohol syndrome and fetal exposure to radiation before 15 weeks gestation.
Trisomy 21 can be detected in the first few months of pregnancy by amniocentesis.
The majority (about 94%) of children with Down Syndrome are born with standard Trisomy 21, which is not hereditary.