A condition caused by an extra copy of chromosome 21, also called trisomy 21.
Trisomy 21 occurs in about 1 in 700 births. It causes intellectual disability of variable degree, characteristic facial features, heart defects and an increased risk of leukaemia and early Alzheimer's. Most cases arise from nondisjunction; a few from translocation.
Prenatal screening includes ultrasound, blood tests and cell-free DNA.
A condition caused by an extra copy of chromosome 21, also called trisomy 21.
Down Syndrome is one of the 54 topics in Genetics. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Turner and Klinefelter Syndromes, Nondisjunction, Chromosomal Mutations.
Life expectancy has risen to around 60 years with better care.
Work through the Beginner topics in Genetics first, such as Heredity, Gene, Allele, then return to Down Syndrome. Intermediate topics assume the Beginner vocabulary.
The closest topics to Down Syndrome are Turner and Klinefelter Syndromes, Nondisjunction, Chromosomal Mutations, Inherited Disorders. Comparing them side by side is a good way to see how the ideas connect.
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Down Syndrome. To practise the whole of Genetics, use the Genetics quiz.
Down Syndrome: A condition caused by an extra copy of chromosome 21, also called trisomy 21. Turner and Klinefelter Syndromes: Sex chromosome aneuploidies: Turner is XO and Klinefelter is XXY. Read both side by side and note what each one explains.
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Turner and Klinefelter Syndromes and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.
Sex chromosome aneuploidies: Turner is XO and Klinefelter is XXY.
🧬 GeneticsFailure of chromosomes to separate in meiosis, producing gametes with extra or missing chromosomes.
🧬 GeneticsLarge structural changes including deletions, duplications, inversions and translocations of chromosome segments.
🧬 GeneticsConditions caused by faulty genes passed through families, such as cystic fibrosis and sickle cell disease.
🧬 Genetics