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Answer:
hope this helps
Explanation:
About 95 percent of the time, Down syndrome is caused by trisomy 21 — the person has three copies of chromosome 21, instead of the usual two copies, in all cells. This is caused by abnormal cell division during the development of the sperm cell or the egg cell.
When we breathe, our respiratory system takes up oxygen and carbon dioxide or other useless gases go out . The oxygen combines with the haemoglobin in the blood of the circulatory system . This is transferred to all the cells of our body to get energy.
The human brain consumes up to 20% of the energy used the entire human body which is any other single organ. the brain represents inly 2%of the body wheight yet it recieves 15% of the cardiac output and 20% of the total body oxygen consumption.
