Question

What is the cause of Down syndrome?

		base pair deletion resulting in a point mutation
		presence of only 45 chromosomes per cell, resulting from the loss of one X chromosome during meiosis
		chromosomal aberration occurring when chromosomes break during synapsis
		presence of 47 chromosomes per cell rather than the normal 46

Answer 1

Down syndrome can be explained as a genetic disorder which happens due to abnormality in cell division. This abnormality results in extra genetic material which causes physical and development related problems in the affected child.

To explain in detail, a human cell consists of 23 pair of chromosomes, contributed from father and mother, each. In a case of abnormal cell division, there happens an extra chromosome 21, which finally results in the total number of chromosomes to 47 instead of 46.

Thus, the final answer is: “presence of 47 chromosomes per cell rather than the normal 46”.