Definition of Down Syndrome:

Down Syndrome can be defined as a condition when a person has an extra copy of a chromosome. Having a supplemental copy of a chromosome is called Trisomy in medical terms, thus, it is a trisomic disorder. It is a genetic condition characterized as an intellectual disability having chromosomal abnormalities.

The human body is composed of many cells; each cell has a nucleus inside it which is responsible for storing the genetic information in terms of genes. Every gene has multiple codons that are responsible for various genetic traits. A typical nucleus consist of 23 pair of chromosomes and half of it inherited from each parent. Down syndrome arises when there is an extra copy of chromosome 21.

Overview of Down syndrome:

Down syndrome is a genetic disease. The malfunction in chromosome leads to the down syndrome in newborns. In humans there are  46 chromosomes, that is 23 pairs of chromosomes are present inside the cell. The diseases arise when there is a presence of 47th chromosome instead of 46 in total, so there is an extra copy of chromosome 21 which can be full or partial.

It is associated with the numerous health problems which include abnormalities in the vision such as refractive anomalies and accommodative anomalies. Some of the physical characteristics associated with Down syndrome include flattened features or stature, bulgy tongue, almond-shaped eyes, loose joints, etc. People with down syndrome have lower IQs and speaks slower as compared to other children.

Statistics of Down Syndrome:

Statistics show that approximately 6000 babies born in the United States have Down syndrome, which is one baby in every 700 have this disease. People suffering from this disorder appears to have a shorter life expectancy, but they can live a healthy lifestyle as other people are living.

Discovery of Down syndrome:

Down syndrome was discovered in the 19th century by the English physician names as John Langdon; He published his work associated with the Down syndrome in 1866, till then he was recognized as the “father” of the syndrome. Researchers in the field of medicine were finding the characteristics of the Down syndrome, later the French physician Jerome Lejeune identified the disease as the chromosomal condition.

extra copy of chromosome 21 - down syndrome

Types of Down syndrome:

  • Trisomy 21
  • Mosaicism
  • Translocation

Trisomy 21

Trisomy 21 is also known as disjunction. Approximately 90% of the population with Down syndrome have trisomy 21. In this condition, the cell consists of three copies of chromosome 21 instead of two. It is the most common type of Down syndrome.


Mosaicism stands for mixture or combination. About 2% of the people with down syndrome have Mosaicism. Mosaicism means a mixture of two types of cells.  A child born with an extra chromosome in some cells, but not all of their cells. The children with mosaic down syndrome are similar to those with down syndrome; they tend to have fewer features as compared to the trisomy 21 due to the presence of a typical number of chromosomes.


Translocation is a condition when there is an extra part of the chromosome. 3% of the population with Down syndrome have a translocation. There are present 46 chromosomes; however, an additional element is present in one chromosome; thus, the extra piece of the chromosome leads to the Down syndrome.

Physical Features Associated with Down Syndrome:

  • Facial features appear to be flat, apparently the bridge of the nose
  • Almont shaped slanted eyes
  • Small head
  • Small ears
  • Tongue seems to be bulgy and tend to stick out of the mouth.
  • Muscle tone is poor
  • Joints are loose
  • Tiny spots are present on the iris of an eye
  • Pink fingers that are small, curved in the direction of the thumb
  • Heights are shorter

Developmental Disabilities with Down syndrome:

  • They tend to have impulsive behaviour
  • They have a shorter attention span
  • They have a poor judgment
  • There learning process is slow
  • They have moderate to lower IQ level

Complications accompanied with down syndrome are as follows:

  • Poor vision
  • Hypothyroidism
  • Obesity
  • Dementia
  • Dislocations
  • Leukaemia
  • Cataracts
  • Heart defects

Causes of Down Syndrome:

Researchers found out that roots of down syndrome are due to an extra chromosome; this addition in the genetic material leads to the disease Down syndrome, but the reason behind the addition of this extra chromosome is unknown yet. The alteration in the cell division and cell development process causes the Down syndrome. During the process of reproduction, chromosomes are transmitted from the parents to the offspring. During cell Development, each cell receives 23 pair of chromosomes, half of them inherited from each parent. Down syndrome arises when one of the chromosomes does not appropriately detach. It results in ending with an extra chromosome or three copies of chromosome 21, which leads to down syndrome. This extra copy causes problems in physical features and brain development.

No one knows what other factors are involved in the development of the disease. One of the factors that result is causing Down syndrome is the mother’s age, Mothers around 35 years of age are at higher chances of having a baby with down syndrome, it can be Trisomy 21 or mosaic down syndrome. Down syndrome can devise from either mother or father, and 5% of the cases have found with father.

Risk Factors of having a baby with Down syndrome:

  • Children with the family history of down syndrome.
  • Maternal age is also a risk factor for Down syndrome.
  • If the parents are the carriers for genetic translocations.
  • If the parents already have a child with down syndrome.
Baby with down syndrome Symptoms

Diagnosis of Down syndrome:

Down syndrome can be predicted during pregnancy. There are two types of tests for diagnosing Down syndrome:

  • Screening
  • Diagnostic tests


Screening in pregnancy predicts if the women have a higher or lower chance of a baby with down syndrome. Screening includes the combination of blood tests in the mother, along with the ultrasound. During an ultrasound, technician look at the fluid behind the baby’s neck, if the baby has extra fluid behind the neck, it indicates the genetic problem. Screening predicts the probability of a baby having down syndrome or not. Screening neither predicts the full impact of down syndrome on a baby

Diagnostic test:

Diagnostic test predicts whether the baby has down syndrome or not. It is performed when the screening results positively. There are different types of diagnostic tests which are as follows:

1-Chorionic villus sampling:

It examines material from the placenta.


It examines the amniotic fluid.

3-Percutaneous Umbilical Blood Sampling (PUBS):

It examines blood from the umbilical cords.

These tests are performed for identifying the changes in the chromosomes to predict down syndrome.

Treatment of Down syndrome:

There is no treatment available for children with down syndrome. Down syndrome is a life long condition, and those babies can have a joyful life if the services provided in their early life are good enough to help them improve their physical and intellectual abilities.

Services to be exercised by the special teachers and therapist for them are as follows:

  • Sensory skills
  • Motor skills
  • Language abilities
  • Cognitive abilities
  • Social skills
  • Self-help skills
  • Speech and physical therapies should also be provided to these children, as they just need extra care and attention.

Lifespan with Down syndrome:

The life span for individuals with Down syndrome is 60 years. The life span for the people with down syndrome has improved from the past years, life expectance for the people with down syndrome was ten years in 1960, and now it has been drastically enhanced to 50 to 60 years.

Frequently Asked Questions:

Question 1
What Is down Syndrome?

Answer: It is a chromosomal disorder where a child is born with an extra chromosome.

Question 2
How can we know if the child has Down Syndrome?

Answer: Before birth, it can be predicted with two types of tests which are Screening and Diagnostic tests. At birth babies with down syndrome have some atypical features such as flat facial features, small ear or head etc.

Question 3
What are the types of Down syndrome?

Answer: There are three different types of Down syndrome

  • Trisomy 21
  • Translocation
  • Mosaicism
Question 4
What causes down syndrome?

Answer: It occurs with an error during the cell division process, also called as disjunction. It occurs in an embryo with chromosome 21 having three copies instead of two.

Question 5
What is the estimated life span for a person with Down syndrome?

Answer: The life expectancy of a person with down syndrome is the average of 60 years.

Question 6
How Down syndrome appears in a child?

Answer: Down syndrome appears when one of the chromosomes does not separate properly; an error occurs during cell division.

Question 7
Does Down Syndrome affect IQ?

Answer: Yes, the children with Down Syndrome have a lower IQ.

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