Most cases of Down syndrome are not inherited, but occur as random events during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction results in reproductive cells with an abnormal number of chromosomes.
Is Down syndrome caused by a dominant or recessive gene?
An autosomal recessive disorder requires two copies of the abnormal gene for the disease or trait to develop. But Down Syndrome itself is neither dominant nor recessive. Trisomy 21 is an extra copy of chromosome 21.
Can you have a Down syndrome baby if it doesnt run in the family?
This can actually happen in two different ways. In one you end up with three separate copies of the extra chromosome. This is the 95% of Down syndrome cases that dont usually run in families. In the other 5% of cases, the extra chromosome gets stuck to another chromosome.
What are the chances of being born with Down syndrome?
Genes are passed from parents to children. About 1 in 700 babies (less than 1 percent) is born with Down syndrome. Many children with Down syndrome lead healthy, active lives.