5.1 PHYSICAL AND MENTAL DISORDERS 109 Do you know where Down syndrome got its name from? Look it up. At conception, a baby gets a total of 46 chromosomes, 23 from each parent. Babies with DS get 47 chromosomes. 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 . This extra genetic material causes both physical and mental delays in the way a child develops. 1 What do you think is their average height? a. 140 cm for males, 130 cm for females. b. 150 cm for males, 140 cm for females. c. 160 cm for males, 150 cm for females. 6 13 19 2 7 14 20 3 8 4 9 15 10 16 21 22 5 11 17 X 12 18 Y 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 . People with DS experience accelerated ageing, i.e. they have conditions that are common in elderly adults. to crawl: gattonare impairment: invalit needle: ago protruding: sporgente slanted: a mandorla 226 diFFicUlties 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 even obesity. Antenatal 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 mother s abdomen.