Lesson Name: Downs Syndrome
LessGood for: 16+ General Public

Equip yourself with the basic knowledge provided in the lesson below and get prepared for *Down Syndrome Quiz
*All 5 questions of Down Syndrome Quiz will be taken from this lesson.

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Down Syndrome

  • Down Syndrome is a genetic disorder that causes some level of learning disability.
  • Down Syndrome is a lifelong condition or a syndrome, not a disease. It has no cure.
  • There is enough evidence that proper education and care can improve the condition.
  • Down Syndrome, also called trisomy 21, is caused by the presence of an extra chromosome.

Image: Courtesy of National Human Genome Research Institute.

What causes Down Syndrome?

  • Genes are the basic unit of heredity. They carry the codes that determine your traits.
  • Genes are made up of DNA. The DNA is coiled and supercoiled to form chromosomes.
  • We inherit 23 chromosomes coming from each parent, meaning 46 in total.
  • A person with Down Syndrome has two copies of chromosome 21, meaning they have 47 chromosomes in total. The extra copy of chromosome 21 in a cell causes Down Syndrome.
  • The cause of the extra (full or partial) chromosome is still unknown.

Why is it called Down Syndrome?

John Langdon Down

Down Syndrome is named after a British physician, John Langdon Down who described the conditions in his scholarly work, published in 1866.

When was a genetic link discovered?

Jérôme Lejeune

In 1959, Jérôme Lejeune, a French pediatrician and geneticist, identified Down Syndrome as a chromosomal condition.

How common is Down Syndrome?

Down Syndrome can happen to anyone. It affects people of all ages, colours, races and religions throughout the world. According to a discreet estimate by World Health Organization, 1 out of every 1000 babies around the world is born with Down Syndrome.

Types of Down Syndrome

Trisomy 21
The most common form of Down Syndrome that accounts for a large percentage of people, about 95%.
With trisomy 21, every cell in the body has an extra copy of chromosome 21.

About 3% of people are affected by translocation Down Syndrome.
In this type of Down Syndrome, part of chromosome 21 attaches to another chromosome instead of being separate.

Mosaic, as appears from the name, means mixture or combination.
It affects about 2% of the people. Some cells in the body are normal while others have trisomy 21.


   Did you know...

Down Syndrome is one of the most common chromosome abnormalities in humans. 
About 80% of children with Down Syndrome are born to women under the age of 35 due to the higher fertility rate. 

Physical features of Down Syndrome

It is important to note that people with Down Syndrome do not all look the same. Some features are specific to those with Down Syndrome such as facial appearance.

Some common physical features of Down Syndrome may include:

  • Short neck and stocky build
  • A flat back of the head
  • Eyes that slant upwards (almond-shaped eyes)
  • A flat nasal bridge
  • A protruding tongue
  • Poor muscle tone
  • Small hands and feet
  • Burchfield’s spots
  • Sandal gap: a large space between the first and second toe

Development delays

It’s a myth that children with Down Syndrome cannot learn. It simply takes more time for them to gain development skills like:

  • sitting
  • reaching
  • standing
  • walking
  • attention
  • judgment
  • speaking


  • Down Syndrome is a lifelong condition.
  • There is no cure for Down Syndrome.
  • There is enough evidence that proper education and care can improve the condition.
  • The quality of life of those with Down Syndrome can be improved with the help of available therapies:
    • Physiotherapy
    • Speech and language therapy
    • Other early intervention programmes

   Did you know...

The average IQ of a young adult with Down Syndrome is about 50*, equivalent to the mental ability of an 8 or 9-year-old child.

* this can vary widely

Health conditions associated with Down Syndrome

The possible health conditions associated with Down Syndrome may include:

  • Autism
  • Depression
  • Ear infection
  • Vision problem
  • Thyroid disorder
  • Heart abnormalities
  • Epileptic spasms in infants
  • Infections such as pneumonia
  • Increased sensitivity to sounds
  • Problems with hormones and glands
  • Risk of developing Alzheimer’s disease increases with age

Living with Down Syndrome

Living with people with Down Syndrome is exactly the same as living with those who don’t. Many adults living with Down Syndrome are able to live on their own or with a family or a roommate just like anyone else.

  • They can form wonderful friendships.
  • They can do sports and enjoy team activities.
  • They can attend school and become active students.
  • They show interest in learning new skills. Some will learn to drive.
  • They can get married to their significant other, just like anyone else.
  • Most people with Down Syndrome lead to healthy and fulfilled lives.
  • People with Down Syndrome can work and participate in decisions.
  • Lots of people with trisomy 21 love to have meaningful relationships.
  • They show the same range of emotions and moods as everyone else.


Chromosome problems such as Down Syndrome can often be diagnosed before birth. Women aged 30–35 years or above might receive genetic non-invasive screening during pregnancy. This is because the chance of having a child with Down Syndrome increases as women age.

Screening tests include:

  • Nuchal translucency testing: At 11–14 weeks, an ultrasound can measure the clear space in folds of tissue behind the neck of a developing fetus.
  • Cell-free DNA: This is a blood test that analyzes fetal DNA present in the mother’s blood.

Diagnostic tests are more accurate for detecting Down Syndrome. A healthcare professional will usually perform such tests inside the uterus. However, they increase the risk of miscarriage, fetal injury, and preterm labour.

Diagnostic tests include:

  • Chorionic villus sampling: At 8–12 weeks, a doctor might obtain a tiny sample of placenta for analysis, using a needle inserted into the cervix or the abdomen.
  • Amniocentesis: At 15–20 weeks, they may obtain a small amount of amniotic fluid for analysis, using a needle inserted into the abdomen.



Children with Down Syndrome need following regular check-ups to monitor their health.

Thyroid Test

Hearing and vision test

Measuring height and weight

Check-ups related to heart problems

Annual Dental review to avoid gums diseases

  • It is worth noting that if one parent has Down Syndrome, there is a 35% to 50% chance that their children would inherit the syndrome. This chance is even higher where both parents have Down Syndrome.

  • Average life expectancy for a person with Down Syndrome is between 50 and 60. A small number of people live into their 70s.

  • Animals closely related to humans can have a similar syndrome. In great apes chromosome 22 corresponds to the human chromosome 21, thus trisomy 22 causes Down Syndrome in apes.

  • The rate of congenital heart disease in newborns with Down Syndrome is around 40% to 42%. Children with Down Syndrome are slightly more likely to develop Leukemia than other children of the same age.

Preferred Language Guide*

When referring to Down Syndrome or people with Down Syndrome, follow these guidelines:

  • People with Down syndrome should always be referred to as people first.
  • Instead of “a Down syndrome child,” it should be “a child with Down syndrome.” Also avoid “Down’s child” and describing the condition as “Down’s,” as in, “He has Down’s.”
  • Down syndrome is a condition or a syndrome, not a disease.
  • People “have” Down syndrome, they do not “suffer from” it and are not “afflicted by” it.
  • “Typically developing” or “typical” is preferred over “normal.”
  • “Intellectual disability” or “cognitive disability” has replaced “mental retardation” as the appropriate term.
  • NDSS strongly condemns the use of the word “retarded” in any derogatory context. Using this word is hurtful and suggests that people with disabilities are not competent.

*Courtesy of ndss National Down Syndrome Society

Down syndrome does not define me

Educate me
Empower me
Disability is not inability
Strength lies in differences
There is a beauty in diversity
See the person, not the disability