Down syndrome is a genetic condition caused when an unusual cell division results in an extra full or partial copy of chromosome 21 A child with down syndrome also may have heart defects and problems with vision and hearing This extra genetic material causes the developmental changes and physical features of down syndrome.
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What is trisomy 21 (down syndrome)
Trisomy 21 is the most common chromosomal anomaly in humans, affecting about 5,000 babies born each year and more than 350,000 people in the united states
Also known as down syndrome, trisomy 21 is a genetic condition caused by an extra chromosome. Trisomy 21 occurs when a developing fetus has three copies of chromosome 21 in every cell instead of the typical two copies This type makes up 95% of all cases of down syndrome. Down syndrome (ds) is the most common genomic disorder of intellectual disability and is caused by trisomy of homo sapiens chromosome 21 (hsa21)
The eponym of the syndrome is from down, who described the clinical aspects of the syndrome in 1866 (ref Trisomy 21 means that each cell in the body has three copies of chromosome 21 instead of the usual two copies Having an extra number 21 chromosome interrupts the normal course of development, causing the characteristic clinical features of down syndrome. Down syndrome is a genetic disorder
It is also called trisomy 21
It includes certain birth defects, learning problems, and facial features
