Down’s syndrome is caused by a chromosomal abnormality in which a person has three copies of chromosome 21 instead of the usual two. This additional genetic material affects development and results in the features associated with the condition.
Down’s syndrome occurs due to a chromosome anomaly in which a person has three copies of chromosome 21 instead of the normal two. This hereditary disorder is also referred to as trisomy 21. The additional chromosome causes an imbalance in the genetic material of the body, potentially leading to the developmental and cognitive traits connected to the syndrome.
| Type | Description | Prevalence | Image |
|---|---|---|---|
| Trisomy 21 | Every cell has an extra chromosome 21. | ~95% | |
| Mosaic | Some cells have 3 copies of chromosome 21; others have 2. | 1–2% | |
| Translocation | Part of chromosome 21 attaches to another chromosome. | 3–4% | |