Down Syndrome

by: Jennifer Alvarado p-4

What is Down Syndrome?

Down Syndrome is a chromosomal disorder. Down Syndrome is the result of when one of three kinds of abnormal cell division occurs, which involves chromosome 21. All three types of cell division abnormalities result in extra genetic material from chromosome 21. It causes a distinct facial appearance, intellectual disability, and developmental delays.
What Causes Trisomy 21 (Down syndrome)?


1866- John Langdon Down, an English physician, associated people with distinct features to decreased intellectual capacity. He named them "Mongoloid" because they looked similar to people from Mongolia.

1959- Dr. Jerome Lejeune, a French geneticist, discovered that Down Syndrome was the result of a chromosomal abnormality. He found that people with Down had 47 chromosomes instead of 46. Soon it was also discovered, that chromosome 21 held an extra part or complete chromosome. This lead to the creation of the term Trisomy 21. Even now, it is still unknown why this happens.

The three genetic differences that cause Down Syndrome

Trisomy 21-
  • The child will have three copies of chromosome 21 instead of two in each of their cells
  • Occurs by abnormal cell division during the development of sperm or egg cells.
  • Happens more than 90% of the time.
Mosaic Down Syndrome-
  • Happens in rare cases.
  • Some cells have an extra copy of chromosome 21.
  • This results in a mixture or mosaic of normal and abnormal cells.
  • Caused by unusual cell division after fertilization.
Translocation Down Syndrome-
  • Occurs when a piece of chromosome 21 becomes attached onto another chromosome.
  • This happens before or during birth.
  • An uncommon form of Down syndrome, occurs only 4% of the time.

Risk Factors

Your risk of having a baby with Down syndrome is higher if:

  • You already have a child with Down Syndrome
  • You or your partner are carriers of the genetic translocation for Down syndrome
  • You are 35 or older

Diagnosis Methods

  • Blood test
  • Ultrasound
  • Cell-free fetal DNA analysis -the cell-free fetal DNA test checks for fetal DNA circulating in the mother's blood.
  • Amniocentesis- A sample of the amniotic fluid surrounding the fetus is withdrawn through a needle inserted into the mother's uterus
  • Chorionic villus sampling (CVS)- In CVS, cells are taken from the placenta and used to analyze the fetal chromosomes.

How can you tell if someone has Down Syndrome?

The characteristics of a person with Down Syndrome are...


  • flattened facial features
  • short neck
  • upward, slanted eyes
  • poor muscle tone
  • short fingers
  • small but broad hands and feet
  • short stature
  • irregular shaped ears
  • protruding tongue
  • excessive flexibility
  • Wide separation between first and second toes
  • Poor judgment
  • Impulsiveness
  • Delayed speech and language development
  • Short attention span
  • Moderate to severe developmental delays
  • Cognitive impairment
  • Slowed learning


The complications of living with Down syndrome can range in severity to mild to extreme and may include the following...

  • Thyroid disease
  • Heart defects
  • Infectious diseases
  • Obesity
  • Seizures
  • Hearing loss
  • Premature aging
  • Skeletal problems
  • Visual problems – crossed-eyes, near or farsightedness, cataracts
  • Leukemia
  • Gastrointestinal abnormalities
  • Early-onset Alzheimer’s disease

Is It Heredity?

Down syndrome is usually not inherited, since it is caused by a mistake during cell division in development of the sperm, egg, or embryo. It does occur though. Translocation Down syndrome is the only form in which, it can be passed from parent to child. There is only a small percentage in which have this, but about fifty percent do get it passed from a parent. The chance of passing on Translocation Down syndrome is dependent upon the gender of the parent, who carries the rearranged chromosome 21. If the male is the carrier, there is about a three percent risk. If the carrier is the female there is a ten to fifteen percent risk.
Down syndrome occurs once in every 800 to 1,000 births, and the majority did not inherit it


Treatments depends on the child's special needs. There is no cure for Down syndrome. Early intervention programs can help children develop sensory, motor, and mental skills. Some treatments that could help people with Down syndrome are...

  • Speech therapy
  • Physical therapy
  • Medication
  • Regular checkups/screenings

How does Down Syndrome affects the individual?

Yes, individuals with Down will have a tough time with many things but, DO NOT FEAR! Expect a bright future for the individuals with down. They're becoming increasingly integrated into society and community organizations. Individuals with Down syndrome possess varying degrees of cognitive delays, from very mild to severe. Due to advances in medical technology, they are also living longer than ever before.

Around the 1920s, children with Down were expected to survive to the age ten. Now, with recent advancements in clinical treatment, as many as 80% of adults with Down syndrome reach age 60, and many live even longer. Many people are accepting and interacting with individuals with Down Syndrome more :)


What is Down Syndrome? | Baby Care Basic | Parents