The What, Why, and How of Down Syndrome

Portrait of beautiful young girls on the playground

In the United States, approximately 400,000 people have Down syndrome.

For just a second, I'm going to take you back to your ninth-grade biology class and explain just a little bit about how the cell works.

In the nucleus of the cell, there are things that are called genes. Genes carry information that eventually decide what our hair color is going to be, what color our skin is going to be, and, really, everything about “us.”

The genes are clumped together into a structure that either resembles an X or a Y, hence the XY and XX business when it comes to having children.

In every nucleus of every cell in the entire body, there are 23 pairs of XY chromosomes if you're a male and XX chromosomes if you're a female—46 chromosomes in total.

Sometimes, however, chromosome 21 may have a third copy made. This disorder is what causes some issues in the genetic makeup of the cell and causes Down syndrome.

According to the National Down Syndrome Society, Down syndrome is the most common genetic condition, being that 1 in 691 children are born with it. In the United States alone, approximately 400,000 people have Down syndrome.

How to spot Down syndrome

In order to identify Down syndrome, diagnoses are given at birth as well as prenatally. When testing for any genetic alterations in the fetus, two options are given: a diagnostic test or a screening test.

Diagnostic tests may cause some apprehension in some mothers. The test is invasive and has a 1% chance of causing a miscarriage. Despite the likelihood of causing miscarriage, the tests are just about as close to 100% accurate as can be.

Screening tests include the typical ultrasound with the accompaniment of a blood test. When looking for indicators of Down syndrome during an ultrasound, doctors will look for what they call “markers,” or common characteristics that the doctor could associate with Down syndrome. Even though the diagnostic test is most often seen as the more accurate of the two tests, the accuracy rate is still extremely high.

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The What, Why, and How of Down Syndrome

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