I. Introduction. 1  The petroleum industry began with the successful drilling of the first commercial oil well in 1859, and the opening of the first refinery two years later to process the crude into kerosene.
The cause of Down syndrome is one of three types of abnormal cell division involving chromosome 21. All three abnormalities result in extra genetic material from chromosome 21, which is responsible for the characteristic features and developmental problems of Down syndrome.
Now you know that Down syndrome is caused by a problem with a chromosome. You might already know that we get our chromosomes from our mother and father. Remember the 23 pairs of chromosomes â half are from your mom and half are from your dad.