Down Syndrome – A Genetic Disorder
Causes of Down syndrome
Down syndrome (DS), also called Trisomy 21, is a genetic disorder caused by the presence of an extra or third copy of chromosome 21 in the genetic information that a child gets at conception.1 This extra genetic material causes both physical and mental delays in the way a child develops.
Physical consequences
People with Down syndrome share some characteristic facial features such as slanted eyes, small ears, a protruding tongue, and low muscle tone. As for their physical development, children with DS learn how to crawl and walk later than other children. They also grow at a slower rate and remain shorter than their peers.
WARM UP
• How dici Down syndrome get its name?
a. Because the intellectual ability of the people who suffer from it is below average.
b. Because of the low mood of the people who suffer from it.
c. Because it takes the name of the doctor who first identified it.
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1 At conception, a baby gets a tota I of 46 chromosomes, 23 from each parent. Babies with DS get 47 chromosomes.
Mental consequences
People with DS suffer from a mild to moderate intellectual disability which affects their ability to learn. Children experience delays in speech and self-care skills, such as feeding, dressing and going to the toilet.
Health consequences
Health problems associated with Down syndrome vary from child to child. Some live healthy lives, while others require medical attention. Almost half of the children born with DS have a congenital heart defect and problems with hearing and vision. Moreover, they can develop respiratory, digestive and thyroid problems and also obesity.
Prenatal detection
Although Down syndrome cannot be prevented, it can be detected with two different types of diagnostic tests of the foetus:
- screening tests, to estimate the risk that a foetus has DS
- diagnostic tests, to state if the foetus really has the condition.
The most common type of diagnostic test is amniocentesis, which is performed between 10 and 12 weeks after conception. It involves the removal of a small amount of amniotic fluid through a needle inserted in the abdomen.
Adult life
People with DS experience accelerated ageing, i.e., they have conditions that are common in elderly adults.
