Name the chromosomal disorder which is caused by the presence of an additional copy of the chromosome number 21.

The non-disjunction during the meiosis in the germ cells of either male or female can result in the abnormality in the chromosome number. One such abnormality is caused when the chromosome number 21 is present in three times instead of a pair in the zygote, called the trisomy of chromosome number 21. Individuals with such a condition are said to be suffering from Down’s Syndrome. It results in physical growth delays, mild to moderate intellectual disability, and characteristic facial features.