There are some genetic disorders that occurs mainly due to disjunction during cell division. A common example is Down Syndrome. They lead to aneuploidy. In case of Down Syndrome this is trisomy, 3 chromosomes are present due to detachment of the microtubule joining the 21st chromosome to centrioles, leading to an extra chromosome in one of the gametes.
But not all chromosomes are similar in tendency to disjunction. That is why Down Syndrome is more common. Why 21st chromosome has more tendency to get disjunction?