FREE ESSAY ON DOWN SYNDROME

DOWN SYNDROME

Down Syndrome or Trisomy 21 as it is also commonly known, is a genetic condition that for
many years has been shrouded in fear, darkness & shame. There is absoultely nothing to
fear, and there never should be any feelings of shame, it is not the persons fault. The
only darkness associated with down syndrome is the ignorance many people have towards
it.
Basically down syndrome means that a person has one extra chromosome in each of the
milions of cells in their body. Instead of 46 chromosomes persons with down syndrome have
47 chromosomes. The extra chromosome happens at the 21st pair, thus TRISOMY 21. It can
and does happen to anyone.
When was down syndrome discovered?
The late 19th century John Langdon Down, an english physician, published an accurate
description of a person with down syndrome. It was published in 1866 and earned Down the
recognition as father of the syndrome.
Throughout the 20th century, advances in medicine & science enabled researchers to
investigate the characteristics of people with down syndrome. It was later determined
that an extra partial or complete 21st chromosome results in the characteristics
associated with down syndrome.
Why is down syndrome referred to as a genetic condition?
The human body is made up of cells, all cells contain a center, called a nucleus, in
which genetic material is stored. This genetic material, knowsn as genes, carries the
codes responsible for all our inherited characteristics.
Genes are grouped along rod-like structures called chromosomes. Normally, the nucleus of
each cell contains 23 pairs of chromosomes, half of which are inherited from each
parent.
In down syndrome, however the cells usually contain not 46, but 47 chromosomes, with the
extra chromosome being a number 21. This excess genetic material in the form of
additional genes along the 21st chromosome, results in down syndrome.
Because 95 percent of all cases of down syndrome oocur because there are three copies of
the 21st chromosome, it is referred to as trisomy 21.
What causes down syndrome?
Down syndrome is usually caused by an error in cell division called nondisjunction.
Nondisjunction is a faulty cell division which results in an embryo with three number 21
chromosomes, instead of two. Prior to it, or at, conception, a pair of number 21
chromosomes in either a sperm or the egg, fail to seperate. As the embryo develops, the
extra chromosome is replicated in every cell of the body.
Why nondisjunction occurs is currently unknown, although it does seem to be related to
advancing maternal age. About 80 percent of children born with down syndrome are born to
women over 35 years of age. This is because younger women have higher fertility rates.
Although nondisjunction can be of paternal origin, this occurs less frequently. Because
this error in a cell division is often present in the egg prior to conception, and women
are born with their complete store of eggs, it has been postulated that some
environmental factors may be implicated in nondisjunction. However, despite years of
research, the cause of nondisjunction is still unknown. There seems to be no connection
between any type of down syndrome and parents activities before or during a pregnancy.
Mosaicism occurs wen nondisjunction of the 21st chromosome takes place in one of the
initial cell divisions after fertilization. When this occurs, there is a mixture of two
types of cells, some containing 46 chromosomes & some containing 47. Because of the
mosaic pattern of the cells, the term mosaicism is used.