I. I met Taylor on my first day of kindergarten and spent the next 8 years being in various classes with him. I knew Taylor had Down syndrome and was different from the way he looked and the way he learned things. But until I was older I didn’t realize that it was all due to one extra chromosome.
II. Today I will discuss what Down syndrome is, how it is diagnosed, and how people can lead a normal life.
I. Down syndrome is a disorder from a chromosome defect.
A. All of you have probably heard of Down Syndrome. But what is it? According to the National Down Syndrome Society webpage that I went to on September 16th, Down syndrome occurs when someone has a full or partial extra copy of chromosome 21.
B. There are three types of Down syndrome; trisomy 21, translocation, and mosaicism. Trisomy 21 results in an embryo with three copies of the chromosome 21 rather than the usual two. In translocation part of chromosome 21 breaks off during cell division and attaches itself to another chromosome. Mosaicism occurs when there is a partial malformation of chromosome 21.
C. One in 691 babies in the United States are born with Down syndrome, making it the most common genetic condition. Approximately 400,000 Americans have Down syndrome and about 6,000 babies with Down syndrome are born in the US each year. Mosaic accounts for 1-2% of all diagnoses, translocation for 2-4% of the diagnoses and trisomy 21 accounts for 95% of children diagnosed with Down syndrome.
Now that you know what down syndrome is, lets take a look at the two ways that Down syndrome diagnosed: prenatally and at birth.
II. There are two tests for Down syndrome that can be done before birth.
A. A prenatal screen can be either a blood test or a 3-d ultrasound. These tests can estimate the chance of the fetus having Down syndrome with almost 100% accuracy.
B. Amniocentesis is a pre-natal test of the amniotic fluid performed...