BY JOrdon Thomas
PictureFigure 1.1 [1]
How Do You Get Down Syndrome?
Down Syndrome, being one of the most serious chromosomal genetic disorder worldwide is caused when three copies of chromosome 21 is formed rather than the normal two chromosomes. This is known to occur when nondisjunction transpires, simply an error during cell devision. Nondisjunction occurs  when a pair of chromosomes fail to separate during egg formation. Therefore, when the egg connects with the ordinary sperm, an embryo is formed, and in this case the the embryo results in having three copies of chromosome 21, resulting in the baby developing down syndrome.  

Meiosis is a significant process in which must be followed as it is an important cell division development process. When the sperm and egg join, fertilization begins. Thus, this is when the DNA (genetic information) is split into each ‘category’; furthermore, the pairs of chromosomes split up and go to different spots. Meiosis also produces gametes (reproductive cell)

From here on, this is known as the starting point of the creation of the nucleus of the daughter cells. In some abnormal situations, one pair of chromomes do not split. (Refer to Figure 1.1)

The cause of Down Syndrome occurs in the case of nondisjunction happening in chromosome 21.  Furthermore, the reproductive cells created by the abnormal meioses carry 22 or 24 chromosomes, when a sperm or egg carries two copies of chromosome 21. This results in the fertilised eggs having 21 chromosomes. [1]

Does Age Impact Trisomy 21?
It has been proven that the older the age of the mother giving birth to a child, the larger the risks are of the child developing DS. As the mother carries 90% chance of Trisomy 21 Case, the older the age of conception, the higher the risk. [1]
Listed below are the statistics of DS development at specific ages:
  • Under age 25, the odds are about 1 in 1,400 [2]
  • Age 30, becomes a 1 in 1000 chance 
  • The odds of having a child with Down syndrome at age 35 are about 1 in 350 [2]
  • At age 40, the odds are about 1 in 100.[2]
  • At age 45, the risk is 1 in 30.
80% of children with Down syndrome are born to women under 35 years of age.  [3]

Although you are unable to prevent Down Syndrome, age has a large contributing factor to the genetic disease. 

Different types of DS
Within Down syndrome itself, there are three different types of this genetic disorder. 

Trisomy 21 being the most common, resulting in 95% of people with this genetic disorder. This occurs when every cell in the body contains an extra chromosome 21. 

Mosaic Down Syndrome on the other hand only occurs in 1-2 % of people with Down Syndrome. Mosaic D.S transpires when an extra chromosome 21 is detected in a number of cells but not all. The other normal cells contain the standard genetic composition.  As Mosaic D.S only appears in a selected number of cells, the outcome of Down Syndrome is weaker , resulting in less obvious physical traits in comparison to someone with Trisomy 21. 

Translocation Down Syndrome is when a part of chromosome 21 is attached to another chromosome. As a result, the baby contains 2 chromome 21 with an additional part of a third chromosome 21. However, Translocation D.S is quite rare as 3-4 % of cases are found with this genetc disorder. 

Future Implications 
Down Sydrome plays a large role in a person’s life from day one. From developing young to growing old this genetic disorder will always be alongside. DS affects everyone significally in the short term and the long term future. In the long term future, their average lifespan is dereased and an average of DS individuals  live to 50 years old. This is an average decrease life expectancy of 3oyears. [5]

Throughout a DS patients life, there are a number of substantial medical awareness’s in which may occur. These may include; respiratory infections, blocked digestive tract, leukaemia, heart defects, hearing loss, hypothyroidism, and eye abnormalities. Because of all these life challenging possibilities, as well as the physical and emotional toll on a sufferer their life span is severely decreased. 

What Causes the Abnormality Link? 
(Physical Symptoms making up the genetic make up of an individual with DS)
Down Syndrome patents look the way they look because simply, chromosomes carry genes, which code for proteins. As Down Syndrome carries two sets of chromome 21, they are carrying two copies of every gene found within the chromosome. Having two genes leads to over expression for the 21 chromomes genes, in which results to increased production of some proteins. Thus, this is where the symptoms of Trisomy 21 (Down Syndrome) begins to develop. [4]
References
  1. Down Syndrome. 2014. Down Syndrome. [ONLINE] Available at:http://learn.genetics.utah.edu/content/disorders/chromosomal/down. [Accessed 17 August 2014].http://www.ucsfhealth.org/education/down_syndrome/ 
  2.  What Is Down Syndrome? - National Down Syndrome Society . 2014.What Is Down Syndrome? - National Down Syndrome Society . [ONLINE] Available at: http://www.ndss.org/Down-Syndrome/What-Is-Down-Syndrome/#sthash.2vRCe4Iv.dpuf. [Accessed 17 August 2014].http://www.ndss.org/Down-Syndrome/What-Is-Down-Syndrome/#sthash.2vRCe4Iv.dpuf  
  3. Down Syndrome. 2014. Down Syndrome. [ONLINE] Available at:http://www.genetic-diseases.net/down-syndrome/. [Accessed 17 August 2014].http://www.genetic-diseases.net/down-syndrome/ 
  4. https://www.google.com.au/search?https://www.google.com.au/search?  q=average+humans+life+expetancy&oq=average+humans+life+expetancy&aqs=chrome..69i57.6559j0j7&sourceid=chrome&es_sm=91&ie=UTF-8 [5]