Down’s syndrome, also known as Trisomy 21, is a genetic disorder which affects around 1 in 1000 children. Each person has 46 chromosomes which are divided into 23 pairs. Each male sperm has 23 chromosomes and each female egg the same, therefore when conception occurs and the sperm fertilises the egg cell, a new being is formed with a full arrangement of chromosomes. Sometimes errors occur thus causing what is known as chromosomal deformities. Down’s syndrome is one of these. During conception, instead of one chromosome 21 from the father (male) and one chromosome 21 from the mother (female) which are combined, a third chromosome 21 combines thus reproducing in each cell of the child’s body and causing an over expression of the genes.
What causes Down’s syndrome?
Until now we don’t know what exactly causes a third chromosome to appear. It can either come from the mother or the father. There is a definite connection to older mothers. However, most children born with Down’s syndrome are born by mothers aged under 35, simply because younger mothers tend to have more children. What we do know is that nobody should be blamed. Nothing that happens before or during pregnancy can cause Down’s syndrome. It is present in all nations, social classes and in all countries all over the world. It can happen to each one of us.
Are there different types of Down’s syndrome?
There are three important types of Down’s syndrome. Your child most probably has Trisomy 21 that is the presence of added genetic material in the extra set of chromosome 21 (3 copies of chromosome 21 instead of 2). Approximately, 95% of people who have Down’s syndrome have Trisomy 21. Approximately, 4% have Translocation Down’s syndrome, in which the extra chromosome 21 is present but attached to a different chromosome in the egg or sperm. Approximately, 1% have Mosaic Down’s syndrome, where some cells have three copies of chromosome 21 and some cells have the usual pair.
What are the characteristics of Down’s syndrome?
Children who are born with Down’s syndrome have certain physical characteristics which vary. Not all children with Down’s syndrome have the same characteristics. Your child may have poorer muscle tone and joint laxity than other children, but this will improve as they age. They may have lower weight than the average birth weight however gain weight at a lower rate than other children (if you are worried about the weight of your child, you can find special weight and growth charts from the Down’s Syndrome Association, www.downs-syndrome.org.uk)
Children with Down’s syndrome often have eyes that slant upwards. Their eyelids may have additional skin folds which appear to exceed an incline (oblique eye fissures on the inner corner of the eyes) but this does not have an impact on their vision. The back of the child’s head may be flatter than usual. Finally, many children with Down’s syndrome have one single crease that goes straight across the palm of their hand. Doctors often search for this crease as a sign that it is a child suffering from Down’s syndrome. It is noteworthy however that some children who don’t have Down’s syndrome also have a similar crease. Children with Down’s syndrome all have a degree of learning difficulty, but this differs greatly from child to child and it is impossible to calculate this degree from birth. Children with Down’s syndrome develop at a slower and more limited rate, but like all children, they will be in a position where they can walk, talk, cycle, read and write.