About Down Syndrome
There are three types of Down syndrome: trisomy 21 (nondisjunction), translocation and mosaicism.
Trisomy 21, the most common type of Down syndrome, occurs when there are three, rather than two, number 21 chromosomes present in every cell of the body. Instead of the usual 46 chromosomes, a person with Down syndrome has 47. It is this additional genetic material that alters the course of development and causes the characteristics associated with the syndrome. Trisomy 21 accounts for 95% of cases.
Translocation accounts for 4% of all cases of Down syndrome. In translocation, part of chromosome 21 breaks off during cell division and attaches to another chromosome, typically chromosome 14. While the total number of chromosomes in the cells remain 46, the presence of an extra part of chromosome 21 causes the characteristics of Down syndrome.
Mosaicism occurs when nondisjunction of chromosome 21 takes place in one - but not all - of the initial cell divisions after fertilization.When this occurs, there is a mixture of two types of cells, some containing the usual 46 chromosomes and others containing 47. Mosaicism accounts for about 1% of all cases of Down syndrome.
One in every 691 babies in the United States is born with Down syndrome, making Down syndrome the most common genetic condition. Approximately 400,000 Americans have Down syndrome and about 6,000 babies with Down syndrome are born in the United States each year.
Here are some great sites that will help to keep you up to date with what is happening in Down syndrome Research.
One of the best ways to promote awareness of Down syndrome and promote the abilities of those who have the disorder is to know the facts and myths. Below are common misconceptions that are held followed by facts to help create understanding.
Myth: Down syndrome is a rare genetic disorder.
Fact: Down syndrome is not rare. The Center for Disease Control estimates 3,357 babies are born with Down syndrome in the U.S. each year.
Myth: Down syndrome is not treatable.
Fact: While there is no cure for Down syndrome, there are many treatments available for the challenges associated with Down syndrome. Through early intervention and related therapies, individuals with Down syndrome are able to greatly improve on their capabilities. Research on Down syndrome is making great strides toward improving, correcting, or even preventing many of the challenges related to Down syndrome.
Myth: People with Down syndrome have severe mental retardation.
Fact: Most people with Down syndrome have only mild to moderate cognitive delays.
Myth: Children with Down syndrome must be placed in separate special education programs.
Fact: Most children with Down syndrome in the United States are integrated into regular school classrooms for varying portions of the day. In some instances, they are fully integrated. Each school system is required by law to provide the least restrictive environment possible for all special needs children. More recently, post-secondary opportunities are being afforded to adults with Down syndrome.
Myth: People with Down syndrome will need to live at home with their parents the rest of their lives.
Fact: A large percentage of adults with Down syndrome live semi-independently with varying levels of support. Some maintain their own homes. Adults with Down syndrome often hold jobs and have romantic relationships.
Myth: People with Down syndrome are always happy.
Fact: People with Down syndrome experience a full range of emotions such as sadness, anger and happiness—just like everyone else.
Myth: Individuals with Down syndrome die at a young age.
Fact: The average life expectancy of an individual with Down syndrome is now 55 years of age. Many live to be 60-70 years of age.
Down Syndrome Association of Pittsburgh :: 700 Bursca Drive, Suite 706 :: Bridgeville, PA 15017 :: (412) 218-2940