Essay: What is Down Syndrome
Down syndrome is one of the major identified syndromes associated with congenital abnormalities in fetuses. Looking back a bit, Stene (2000), states that developmental abnormalities to the embryo usually involve only small DNA mutations affecting individual or a few genes. In this regard, major chromosomal abnormalities are usually trisomy; trisomy 21and trisomy 18 that reflect Down syndrome and Edwards syndrome respectively. But, this paper shall majorly concentrate on the Down syndrome.
Since 1866 naming of Down syndrome by British doctor John Langdon Down, the syndrome remains the major cause for congenital abnormalities exhibited from embryos to children even adults. Ideally, Down syndrome is caused by the presence of all or part of an extra 21st chromosome, hence also referred to as trisomy 21. Therefore, this extra copy of the genetic material on the 21st chromosome either in whole (trisomy 21) or part makes Down syndrome chromosomal abnormality. The justification for a syndrome is due to this extra copy is opposed to the normal genetic of human karyotype is designated as 46, XX or 46, XY. This designation implies that there are 46 chromosomes with an XX arrangement for females and 46 chromosomes with an XY arrangement for males (Duyune S et al 316). However, there is variation in chromosomal error in Down syndrome resulting to three categories.
The better side of this syndrome is that it is so far known syndrome to be the only trisomy compatible with life. In terms of prevalence, Down syndrome mainly 95 percent of trisomy 21 is estimated at 1 per 800 births in general. But, in the year 2006 and 2007 this estimate fell to 1 per 733 live births in the United States with a total of 5429 new cases per year. The research also indicates that maternal age influences the risk of an embryo developing Down syndrome. For instance, at maternal ages 20 to 24 years; 40 years; 49 years the risk is 1/1490; 1/60; 1/11 respectively (age risk statistics table1). Unfortunately, women under the age of 35 years accounts to 80% of children with Down syndrome.