if non homologous chromosomes exchange segments it is called translocation. In humans translocation is common in 13th and 14th chromosome. Creates infertility. Down syndrome chromosome 21 joins chromosome 14. Also create cancer. non disjunction can be monosomy or trisomy. Rises probability with age 1 out of 1500 if the woman is below 25 and 1/100 at 40 age.Olsen 2003.