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.
Â· just now. 1  Down syndrome is caused by a problem with a babyâs chromosomes that happens long before the baby is born. 2  Down syndrome is a chromosomal disorder where an extra copy of chromosome 21 is made, the term is called trisomy 21. 3  It is caused by trisomy, having 3 of the same chromosomes (chromosome 21) One usually have 2 of the same chromosomes, but down syndrome has 3. i a chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. one extra chromosome.