Intermediate
Technical
In the Industry Vocabulary Test
trisomy 21
Chromosomal condition caused by an extra copy of chromosome 21, resulting in Down syndrome.
Full Definition
Trisomy 21 is the most common viable autosomal trisomy, characterized by the presence of three copies of chromosome 21 instead of the normal two copies. This chromosomal abnormality causes Down syndrome, which is associated with intellectual disability, characteristic facial features, and increased risk of certain medical conditions including congenital heart defects, gastrointestinal abnormalities, and thyroid dysfunction. The condition can be detected through prenatal screening and diagnostic testing, with risk increasing with advanced maternal age.
Usage
Usage note: Use 'trisomy 21' rather than 'Down syndrome' in formal genetic reports.
In Context
- "Genetic counseling was provided following the diagnosis of trisomy 21 on amniocentesis." — Genetic counseling notes
Also known as
Down syndrome
Don't confuse with
trisomy 18
trisomy 13