Down Syndrome (Tri-21)

Shannon Hensley

What is Down Syndrome?

"Down syndrome is a chromosomal disorder caused by an error in cell division that results in an extra 21st chromosome."

What happens?

Growth and development can be slowed ranging from mild to moderate developmental disabilities.


Down syndrome affects the whole body however, it is most prominent in facial features. Some of these are: Upward slanted eyes, low muscle tone, small stature, short neck, flat nasal bridge, protruding tongue, white spots on the iris, single deep crease in the palm of the hand. Intellectual and developmental characteristics: short attention span, poor judgement, impulsive behavior, slow learning, and delayed speech and language development.


An error in cell division causes an extra 21st chromosome.

It is not considered a mutation because, in the meiotic division the chromosome fails to separate in the sperm or egg causing it to have three instead of two.

How do you get the disorder?

It is not a sex-linked disorder, it is a chromosomal disorder on the 21st chromosome. Down syndrome is neither dominant or recessive because it is not inherited.

Can/how is it treated?

Early intervention can include people of these professions: special educators, speech therapists, occupational therapists, physical therapists, and social workers. Some Down syndrome patients take amino acid supplements, supplementary vitamins and minerals, and thyroid hormones that affect their brain activity and increase their intellectual abilities.

How is it diagnosed?

“Down syndrome can be diagnosed in infancy based on the characteristic clinical findings. When Down syndrome is suspected in a person, a genetic test called a chromosome analysis is performed on a blood or skin sample to look for an extra chromosome 21 (trisomy 21). Trisomy 21 means that each cell in the body has three copies of chromosome 21 instead of the usual two copies.”

Population Effects

1 in every 691 babies in the U.S. is born with Down Syndrome that's approximately 6000 births a year. It is not more common in one specific group of people and it is the most common chromosomal condition.

What I discovered..

I learned that it isn't an inherited disorder and the older a woman gets the more likely her chances of having a baby with Down syndrome becomes. I also learned it is the most common of all chromosomal disorders.
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Lib's Life - Down Syndrome Documentary
Understanding Down Syndrome (Baby Health Guru)

citations and references

Crosta, Peter. "Down Syndrome: Facts, Symptoms and Characteristics." Medical News Today. MediLexicon, Intl., 22 Apr. 2016. Web.

22 Apr. 2016.

Bull, M. J., & the Committee on Genetics. (2011). Health supervision for children with Down syndrome. Pediatrics, 128, 393–406 22 Apr. 2016. Web.

National Human Genome Research Institute. (2010). Learning about Down syndrome. Retrieved June 11, 2012, from