Lauren Simmonslek69@wildcats.unh.eduUniversity of New Hampshire at Manchester

This photo is from the Google public domain and is available for public use.


Down Syndrome is caused by the trisomy of chromosome 21 that occurs during embryonic development and is the most common chromosomal defect in humans. It is also the leading cause of intellectual disabilities and affects around one in 800 individuals (Wilcock & Griffin, 2013). Past research has conducted studies regarding the link between Alzheimer's Disease and Down Syndrome, which includes the amyloid-β (Aβ) plaques as well as amyloid precursor proteins (APP) in the brain (Wang, Huang, Bu and Xu, 2014). There have also been studies done investigating the dosage effect hypothesis associated with the causation of several different Down Syndrome phenotypes (Yahya-Graison et. al., 2007). Along with intellectual disablities, Down Syndrome causes physical characteristics as well as the following health issues according to the NICHD (2014):

  • Autoimmune diseases

  • Congenital heart disease

  • Early onset Dementia

  • Hypotonia

  • Epilepsy

  • Celiac disease

  • Increased risk of cancer

  • High blood pressure
    This photo is from the Google public domain and is available for public use.

In the photograph to the right, the physical characteristics are demonstrated in a young boy with Down Syndrome. A flat, wide nose, almond-shaped eyes spread far apart, as well as a large mouth. Down Syndrome can also cause a short stature as well as small hands and feet (NICHD, 2014). The figure to the left demonstrates the trisomy, or extra, 21st chromosome of the human genome. In a normal human genome, each individual has two pairs of each chromosomes whereas this individual has three sets of chromosome 21 resulting in the development of Down Syndrome. The 21st chromosome is estimated to contain 352 genes (Lockstone et al., 2007). It has also been found that trisomic genes on chromosome 21 demonstrate that 27% of these genes are overexpressed in Down Syndrome patients. This is a much higher percentage compared to other trisomic chromosomes that demonstrated a median value of merely 4.3% of gene overexpression (Lockstone et al., 2007). This creates a possible conclusion that chromosome 21 causes the highest quantity of overexpressed genes when it is trisomic which could explain why Down Syndrome is a disease that affects so many parts of the human body; physique, brain, immune system, etc.

Research Questions:

What genes and proteins are responsible in Down Syndrome patients for early onset Alzheimer's Disease?
What genotypes are responsible for the different phenotypes of Down Syndrome?

Primary Research Methods Data Data Analysis References