Chromosome balance translocation, there are 23 pairs (46) of chromosomes in human cells. The number and structure of chromosomes are relatively constant and cannot be just a little more or a little less, otherwise there will be changes, for example, a congenitally stupid child has one more than normal on chromosome 21. It is possible to reduce the fertility of offspring. Patients with chromosomal balance translocations have a high miscarriage rate or a low pregnancy rate. The solution to this problem is to do third generation IVF, or PGD technology, which screens the chromosomes of the embryos and selects healthy embryos for transfer. This translocation results in an “internal move” of the chromosomal genetic material. However, in a single cell, the total number of chromosomes remains the same and the genes contained are not missing, so the person does not show abnormal symptoms, has normal appearance and intelligence, and does not have any developmental defects; they are just carriers of the translocated chromosomes. When examining the chromosomes of the man mentioned above, we found that the total number of chromosomes seemed to be only 45. After careful analysis, we found that one of chromosome 13 was “missing” and the other was twice as long as normal, indicating that chromosome 13 in his cells was translocated and two chromosomes 13 were merged into one. Another type of chromosome balancing translocation is when a small segment of one chromosome swaps places with a small segment of another chromosome. For example, a part of chromosome 15 moves to chromosome 3, while a small segment of chromosome 3 moves to chromosome 15. Thus, one chromosome of each of these two pairs is normal and the other is abnormal. At fertilization, if all the chromosomes provided by the patient with balanced chromosomal translocation are normal, the embryo is normal and develops into a healthy child, and if 2 or 1 of the chromosomes provided by him/her are abnormal, the resulting embryo has unbalanced chromosomal translocation.